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	$182.98	4.121%	$190.5206	$190.52	$190.50	$190.50
Purchase #2	$219.51	3.317%	$226.7911	$226.79	$226.80	$226.80
Purchase #3	$184.43	3.188%	$190.3096	$190.31	$190.30	$190.30
Purchase #4	$37.74	3.750%	$39.1553	$39.16	$39.15	$39.20
Purchase #5	$245.95	7.694%	$264.8734	$264.87	$264.85	$264.90
Purchase #6	$37.98	4.828%	$39.8137	$39.81	$39.80	$39.80
Purchase #7	$99.68	12.434%	$112.0742	$112.07	$112.05	$112.10
7 purchase totals =	$1,008.27		$1,063.5379	$1,063.53	$1,063.45	$1,063.60