Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$119.83	6.291%	$127.3685	$127.37	$127.35	$127.40
Purchase #2	$171.50	11.454%	$191.1436	$191.14	$191.15	$191.10
Purchase #3	$184.87	9.871%	$203.1185	$203.12	$203.10	$203.10
Purchase #4	$103.31	8.785%	$112.3858	$112.39	$112.40	$112.40
Purchase #5	$198.50	13.232%	$224.7655	$224.77	$224.75	$224.80
Purchase #6	$94.54	10.317%	$104.2937	$104.29	$104.30	$104.30
Purchase #7	$171.77	7.866%	$185.2814	$185.28	$185.30	$185.30
7 purchase totals =	$1,044.32		$1,148.3570	$1,148.36	$1,148.35	$1,148.40