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	$247.28	3.428%	$255.7568	$255.76	$255.75	$255.80
Purchase #2	$115.30	3.777%	$119.6549	$119.65	$119.65	$119.70
Purchase #3	$210.29	11.137%	$233.71	$233.71	$233.70	$233.70
Purchase #4	$131.93	10.164%	$145.3394	$145.34	$145.35	$145.30
Purchase #5	$101.45	3.865%	$105.371	$105.37	$105.35	$105.40
Purchase #6	$149.95	12.593%	$168.8332	$168.83	$168.85	$168.80
Purchase #7	$215.72	9.413%	$236.0257	$236.03	$236.05	$236.00
7 purchase totals =	$1,171.92		$1,264.6910	$1,264.69	$1,264.70	$1,264.70