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	$20.41	11.848%	$22.8282	$22.83	$22.85	$22.80
Purchase #2	$89.38	11.424%	$99.5908	$99.59	$99.60	$99.60
Purchase #3	$193.68	5.450%	$204.2356	$204.24	$204.25	$204.20
Purchase #4	$218.93	4.824%	$229.4912	$229.49	$229.50	$229.50
Purchase #5	$244.72	4.843%	$256.5718	$256.57	$256.55	$256.60
Purchase #6	$81.42	8.511%	$88.3497	$88.35	$88.35	$88.30
Purchase #7	$133.33	5.279%	$140.3685	$140.37	$140.35	$140.40
7 purchase totals =	$981.87		$1,041.4358	$1,041.44	$1,041.45	$1,041.40