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	$51.34	4.282%	$53.5384	$53.54	$53.55	$53.50
Purchase #2	$25.92	4.511%	$27.0893	$27.09	$27.10	$27.10
Purchase #3	$26.39	4.451%	$27.5646	$27.56	$27.55	$27.60
Purchase #4	$92.36	5.314%	$97.268	$97.27	$97.25	$97.30
Purchase #5	$118.28	5.468%	$124.7476	$124.75	$124.75	$124.70
Purchase #6	$100.52	10.738%	$111.3138	$111.31	$111.30	$111.30
Purchase #7	$144.51	3.541%	$149.6271	$149.63	$149.65	$149.60
7 purchase totals =	$559.32		$591.1488	$591.15	$591.15	$591.10