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	$42.34	6.733%	$45.1908	$45.19	$45.20	$45.20
Purchase #2	$106.34	4.864%	$111.5124	$111.51	$111.50	$111.50
Purchase #3	$242.39	10.116%	$266.9102	$266.91	$266.90	$266.90
Purchase #4	$152.33	4.260%	$158.8193	$158.82	$158.80	$158.80
Purchase #5	$219.44	7.139%	$235.1058	$235.11	$235.10	$235.10
Purchase #6	$155.84	11.692%	$174.0608	$174.06	$174.05	$174.10
Purchase #7	$212.38	5.169%	$223.3579	$223.36	$223.35	$223.40
7 purchase totals =	$1,131.06		$1,214.9572	$1,214.96	$1,214.90	$1,215.00