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	$227.86	3.386%	$235.5753	$235.58	$235.60	$235.60
Purchase #2	$61.83	9.854%	$67.9227	$67.92	$67.90	$67.90
Purchase #3	$34.41	9.220%	$37.5826	$37.58	$37.60	$37.60
Purchase #4	$48.35	9.433%	$52.9109	$52.91	$52.90	$52.90
Purchase #5	$188.65	3.229%	$194.7415	$194.74	$194.75	$194.70
Purchase #6	$41.31	10.191%	$45.5199	$45.52	$45.50	$45.50
Purchase #7	$107.53	5.240%	$113.1646	$113.16	$113.15	$113.20
7 purchase totals =	$709.94		$747.4175	$747.41	$747.40	$747.40