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	$75.88	8.464%	$82.3025	$82.30	$82.30	$82.30
Purchase #2	$168.33	7.442%	$180.8571	$180.86	$180.85	$180.90
Purchase #3	$193.27	8.571%	$209.8352	$209.84	$209.85	$209.80
Purchase #4	$139.76	7.628%	$150.4209	$150.42	$150.40	$150.40
Purchase #5	$218.54	5.221%	$229.95	$229.95	$229.95	$230.00
Purchase #6	$74.96	13.248%	$84.8907	$84.89	$84.90	$84.90
Purchase #7	$154.54	4.769%	$161.91	$161.91	$161.90	$161.90
7 purchase totals =	$1,025.28		$1,100.1664	$1,100.17	$1,100.15	$1,100.20