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	$54.46	8.867%	$59.289	$59.29	$59.30	$59.30
Purchase #2	$12.40	13.681%	$14.0964	$14.10	$14.10	$14.10
Purchase #3	$60.38	10.573%	$66.764	$66.76	$66.75	$66.80
Purchase #4	$148.58	7.309%	$159.4397	$159.44	$159.45	$159.40
Purchase #5	$166.73	8.261%	$180.5036	$180.50	$180.50	$180.50
Purchase #6	$61.88	13.464%	$70.2115	$70.21	$70.20	$70.20
Purchase #7	$148.64	13.314%	$168.4299	$168.43	$168.45	$168.40
7 purchase totals =	$653.07		$718.7341	$718.73	$718.75	$718.70