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	$57.42	8.466%	$62.2812	$62.28	$62.30	$62.30
Purchase #2	$210.50	13.350%	$238.6018	$238.60	$238.60	$238.60
Purchase #3	$105.59	13.459%	$119.8014	$119.80	$119.80	$119.80
Purchase #4	$233.29	6.508%	$248.4725	$248.47	$248.45	$248.50
Purchase #5	$232.32	5.155%	$244.2961	$244.30	$244.30	$244.30
Purchase #6	$42.33	9.482%	$46.3437	$46.34	$46.35	$46.30
Purchase #7	$74.74	4.831%	$78.3507	$78.35	$78.35	$78.40
7 purchase totals =	$956.19		$1,038.1474	$1,038.14	$1,038.15	$1,038.20