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	$11.61	8.114%	$12.552	$12.55	$12.55	$12.60
Purchase #2	$160.27	12.191%	$179.8085	$179.81	$179.80	$179.80
Purchase #3	$12.73	12.571%	$14.3303	$14.33	$14.35	$14.30
Purchase #4	$237.62	9.394%	$259.942	$259.94	$259.95	$259.90
Purchase #5	$104.83	6.629%	$111.7792	$111.78	$111.80	$111.80
Purchase #6	$115.69	12.722%	$130.4081	$130.41	$130.40	$130.40
Purchase #7	$31.36	3.174%	$32.3554	$32.36	$32.35	$32.40
7 purchase totals =	$674.11		$741.1755	$741.18	$741.20	$741.20