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	$156.75	12.211%	$175.8907	$175.89	$175.90	$175.90
Purchase #2	$38.34	4.496%	$40.0638	$40.06	$40.05	$40.10
Purchase #3	$31.69	4.449%	$33.0999	$33.10	$33.10	$33.10
Purchase #4	$96.40	8.734%	$104.8196	$104.82	$104.80	$104.80
Purchase #5	$220.35	5.605%	$232.7006	$232.70	$232.70	$232.70
Purchase #6	$88.45	12.331%	$99.3568	$99.36	$99.35	$99.40
Purchase #7	$49.44	10.517%	$54.6396	$54.64	$54.65	$54.60
7 purchase totals =	$681.42		$740.5710	$740.57	$740.55	$740.60