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	$77.57	4.188%	$80.8186	$80.82	$80.80	$80.80
Purchase #2	$33.83	11.694%	$37.7861	$37.79	$37.80	$37.80
Purchase #3	$165.60	11.680%	$184.9421	$184.94	$184.95	$184.90
Purchase #4	$234.88	7.110%	$251.58	$251.58	$251.60	$251.60
Purchase #5	$247.50	13.655%	$281.2961	$281.30	$281.30	$281.30
Purchase #6	$90.25	6.413%	$96.0377	$96.04	$96.05	$96.00
Purchase #7	$100.70	10.486%	$111.2594	$111.26	$111.25	$111.30
7 purchase totals =	$950.33		$1,043.7200	$1,043.73	$1,043.75	$1,043.70