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	$175.85	11.550%	$196.1607	$196.16	$196.15	$196.20
Purchase #2	$144.51	11.672%	$161.3772	$161.38	$161.40	$161.40
Purchase #3	$36.98	3.754%	$38.3682	$38.37	$38.35	$38.40
Purchase #4	$161.46	8.115%	$174.5625	$174.56	$174.55	$174.60
Purchase #5	$122.90	8.647%	$133.5272	$133.53	$133.55	$133.50
Purchase #6	$55.78	5.324%	$58.7497	$58.75	$58.75	$58.70
Purchase #7	$103.46	7.793%	$111.5226	$111.52	$111.50	$111.50
7 purchase totals =	$800.94		$874.2681	$874.27	$874.25	$874.30