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	$150.86	5.543%	$159.2222	$159.22	$159.20	$159.20
Purchase #2	$84.79	6.419%	$90.2327	$90.23	$90.25	$90.20
Purchase #3	$77.84	11.442%	$86.7465	$86.75	$86.75	$86.70
Purchase #4	$19.95	9.441%	$21.8335	$21.83	$21.85	$21.80
Purchase #5	$159.88	5.487%	$168.6526	$168.65	$168.65	$168.70
Purchase #6	$223.72	13.180%	$253.2063	$253.21	$253.20	$253.20
Purchase #7	$89.56	5.413%	$94.4079	$94.41	$94.40	$94.40
7 purchase totals =	$806.60		$874.3017	$874.30	$874.30	$874.20