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	$54.46	12.348%	$61.1847	$61.18	$61.20	$61.20
Purchase #2	$120.83	8.715%	$131.3603	$131.36	$131.35	$131.40
Purchase #3	$215.93	13.865%	$245.8687	$245.87	$245.85	$245.90
Purchase #4	$244.93	11.778%	$273.7779	$273.78	$273.80	$273.80
Purchase #5	$131.28	7.822%	$141.5487	$141.55	$141.55	$141.50
Purchase #6	$22.43	5.713%	$23.7114	$23.71	$23.70	$23.70
Purchase #7	$215.75	3.603%	$223.5235	$223.52	$223.50	$223.50
7 purchase totals =	$1,005.61		$1,100.9752	$1,100.97	$1,100.95	$1,101.00