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	$190.85	9.792%	$209.538	$209.54	$209.55	$209.50
Purchase #2	$17.71	10.127%	$19.5035	$19.50	$19.50	$19.50
Purchase #3	$201.73	11.609%	$225.1488	$225.15	$225.15	$225.10
Purchase #4	$98.64	11.142%	$109.6305	$109.63	$109.65	$109.60
Purchase #5	$78.25	4.399%	$81.6922	$81.69	$81.70	$81.70
Purchase #6	$39.73	12.805%	$44.8174	$44.82	$44.80	$44.80
Purchase #7	$135.71	13.810%	$154.4516	$154.45	$154.45	$154.50
7 purchase totals =	$762.62		$844.7820	$844.78	$844.80	$844.70