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	$145.26	12.153%	$162.9134	$162.91	$162.90	$162.90
Purchase #2	$230.25	8.700%	$250.2818	$250.28	$250.30	$250.30
Purchase #3	$36.54	7.635%	$39.3298	$39.33	$39.35	$39.30
Purchase #4	$79.97	13.405%	$90.69	$90.69	$90.70	$90.70
Purchase #5	$110.53	6.214%	$117.3983	$117.40	$117.40	$117.40
Purchase #6	$142.76	6.353%	$151.8295	$151.83	$151.85	$151.80
Purchase #7	$148.54	3.267%	$153.3928	$153.39	$153.40	$153.40
7 purchase totals =	$893.85		$965.8356	$965.83	$965.90	$965.80