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	$31.26	6.397%	$33.2597	$33.26	$33.25	$33.30
Purchase #2	$116.58	9.395%	$127.5327	$127.53	$127.55	$127.50
Purchase #3	$196.84	10.254%	$217.024	$217.02	$217.00	$217.00
Purchase #4	$71.97	12.283%	$80.8101	$80.81	$80.80	$80.80
Purchase #5	$78.43	6.708%	$83.6911	$83.69	$83.70	$83.70
Purchase #6	$64.74	9.558%	$70.9278	$70.93	$70.95	$70.90
Purchase #7	$191.33	12.833%	$215.8834	$215.88	$215.90	$215.90
7 purchase totals =	$751.15		$829.1288	$829.12	$829.15	$829.10