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	$106.32	9.485%	$116.4045	$116.40	$116.40	$116.40
Purchase #2	$51.42	13.573%	$58.3992	$58.40	$58.40	$58.40
Purchase #3	$243.53	4.834%	$255.3022	$255.30	$255.30	$255.30
Purchase #4	$232.63	13.537%	$264.1211	$264.12	$264.10	$264.10
Purchase #5	$70.44	11.260%	$78.3715	$78.37	$78.35	$78.40
Purchase #6	$183.67	5.869%	$194.4496	$194.45	$194.45	$194.40
Purchase #7	$119.64	7.810%	$128.9839	$128.98	$129.00	$129.00
7 purchase totals =	$1,007.65		$1,096.0320	$1,096.02	$1,096.00	$1,096.00