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	$147.91	12.266%	$166.0526	$166.05	$166.05	$166.10
Purchase #2	$35.68	11.121%	$39.648	$39.65	$39.65	$39.60
Purchase #3	$70.97	11.150%	$78.8832	$78.88	$78.90	$78.90
Purchase #4	$139.80	4.799%	$146.509	$146.51	$146.50	$146.50
Purchase #5	$190.57	9.715%	$209.0839	$209.08	$209.10	$209.10
Purchase #6	$110.52	7.538%	$118.851	$118.85	$118.85	$118.90
Purchase #7	$110.73	11.537%	$123.5049	$123.50	$123.50	$123.50
7 purchase totals =	$806.18		$882.5326	$882.52	$882.55	$882.60