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	$46.63	3.152%	$48.0998	$48.10	$48.10	$48.10
Purchase #2	$66.67	9.125%	$72.7536	$72.75	$72.75	$72.80
Purchase #3	$158.43	11.451%	$176.5718	$176.57	$176.55	$176.60
Purchase #4	$139.28	4.611%	$145.7022	$145.70	$145.70	$145.70
Purchase #5	$247.97	9.396%	$271.2693	$271.27	$271.25	$271.30
Purchase #6	$142.62	11.582%	$159.1382	$159.14	$159.15	$159.10
Purchase #7	$182.71	3.143%	$188.4526	$188.45	$188.45	$188.50
7 purchase totals =	$984.31		$1,061.9875	$1,061.98	$1,061.95	$1,062.10