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	$169.75	12.395%	$190.7905	$190.79	$190.80	$190.80
Purchase #2	$40.65	11.560%	$45.3491	$45.35	$45.35	$45.30
Purchase #3	$68.76	9.651%	$75.396	$75.40	$75.40	$75.40
Purchase #4	$152.53	7.802%	$164.4304	$164.43	$164.45	$164.40
Purchase #5	$226.29	11.172%	$251.5711	$251.57	$251.55	$251.60
Purchase #6	$219.68	8.553%	$238.4692	$238.47	$238.45	$238.50
Purchase #7	$48.73	5.434%	$51.378	$51.38	$51.40	$51.40
7 purchase totals =	$926.39		$1,017.3843	$1,017.39	$1,017.40	$1,017.40