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	$78.57	6.297%	$83.5176	$83.52	$83.50	$83.50
Purchase #2	$196.33	12.331%	$220.5395	$220.54	$220.55	$220.50
Purchase #3	$21.27	3.653%	$22.047	$22.05	$22.05	$22.00
Purchase #4	$191.99	12.248%	$215.5049	$215.50	$215.50	$215.50
Purchase #5	$152.49	12.635%	$171.7571	$171.76	$171.75	$171.80
Purchase #6	$246.53	7.408%	$264.7929	$264.79	$264.80	$264.80
Purchase #7	$214.82	13.810%	$244.4866	$244.49	$244.50	$244.50
7 purchase totals =	$1,102.00		$1,222.6456	$1,222.65	$1,222.65	$1,222.60