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	$102.28	8.789%	$111.2694	$111.27	$111.25	$111.30
Purchase #2	$131.82	12.530%	$148.337	$148.34	$148.35	$148.30
Purchase #3	$79.31	6.406%	$84.3906	$84.39	$84.40	$84.40
Purchase #4	$219.38	7.417%	$235.6514	$235.65	$235.65	$235.70
Purchase #5	$233.39	8.757%	$253.828	$253.83	$253.85	$253.80
Purchase #6	$106.94	6.729%	$114.136	$114.14	$114.15	$114.10
Purchase #7	$70.34	11.641%	$78.5283	$78.53	$78.55	$78.50
7 purchase totals =	$943.46		$1,026.1407	$1,026.15	$1,026.20	$1,026.10