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	$62.81	4.316%	$65.5209	$65.52	$65.50	$65.50
Purchase #2	$189.65	11.706%	$211.8504	$211.85	$211.85	$211.90
Purchase #3	$21.53	6.413%	$22.9107	$22.91	$22.90	$22.90
Purchase #4	$37.29	3.814%	$38.7122	$38.71	$38.70	$38.70
Purchase #5	$201.45	11.565%	$224.7477	$224.75	$224.75	$224.70
Purchase #6	$168.64	6.271%	$179.2154	$179.22	$179.20	$179.20
Purchase #7	$97.97	11.872%	$109.601	$109.60	$109.60	$109.60
7 purchase totals =	$779.34		$852.5583	$852.56	$852.50	$852.50