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	$101.49	8.179%	$109.7909	$109.79	$109.80	$109.80
Purchase #2	$96.36	10.515%	$106.4923	$106.49	$106.50	$106.50
Purchase #3	$176.61	5.496%	$186.3165	$186.32	$186.30	$186.30
Purchase #4	$36.39	11.528%	$40.585	$40.59	$40.60	$40.60
Purchase #5	$135.57	11.719%	$151.4574	$151.46	$151.45	$151.50
Purchase #6	$244.84	7.845%	$264.0477	$264.05	$264.05	$264.00
Purchase #7	$178.41	3.488%	$184.6329	$184.63	$184.65	$184.60
7 purchase totals =	$969.67		$1,043.3227	$1,043.33	$1,043.35	$1,043.30