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	$159.29	3.816%	$165.3685	$165.37	$165.35	$165.40
Purchase #2	$88.64	8.361%	$96.0512	$96.05	$96.05	$96.10
Purchase #3	$150.69	10.498%	$166.5094	$166.51	$166.50	$166.50
Purchase #4	$90.27	11.298%	$100.4687	$100.47	$100.45	$100.50
Purchase #5	$247.69	9.461%	$271.124	$271.12	$271.10	$271.10
Purchase #6	$65.29	5.139%	$68.6453	$68.65	$68.65	$68.60
Purchase #7	$237.40	8.198%	$256.8621	$256.86	$256.85	$256.90
7 purchase totals =	$1,039.27		$1,125.0292	$1,125.03	$1,124.95	$1,125.10