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	$142.36	7.669%	$153.2776	$153.28	$153.30	$153.30
Purchase #2	$192.43	10.350%	$212.3465	$212.35	$212.35	$212.30
Purchase #3	$31.82	4.167%	$33.1459	$33.15	$33.15	$33.10
Purchase #4	$228.83	3.861%	$237.6651	$237.67	$237.65	$237.70
Purchase #5	$45.72	5.864%	$48.401	$48.40	$48.40	$48.40
Purchase #6	$214.55	9.649%	$235.2519	$235.25	$235.25	$235.30
Purchase #7	$154.76	7.185%	$165.8795	$165.88	$165.90	$165.90
7 purchase totals =	$1,010.47		$1,085.9675	$1,085.98	$1,086.00	$1,086.00