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	$165.85	5.684%	$175.2769	$175.28	$175.30	$175.30
Purchase #2	$180.46	3.705%	$187.146	$187.15	$187.15	$187.10
Purchase #3	$204.52	7.448%	$219.7526	$219.75	$219.75	$219.80
Purchase #4	$235.37	8.693%	$255.8307	$255.83	$255.85	$255.80
Purchase #5	$227.39	6.581%	$242.3545	$242.35	$242.35	$242.40
Purchase #6	$66.90	7.110%	$71.6566	$71.66	$71.65	$71.70
Purchase #7	$70.29	11.329%	$78.2532	$78.25	$78.25	$78.30
7 purchase totals =	$1,150.78		$1,230.2705	$1,230.27	$1,230.30	$1,230.40