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	$106.44	3.477%	$110.1409	$110.14	$110.15	$110.10
Purchase #2	$128.47	9.192%	$140.279	$140.28	$140.30	$140.30
Purchase #3	$31.89	3.846%	$33.1165	$33.12	$33.10	$33.10
Purchase #4	$10.44	13.496%	$11.849	$11.85	$11.85	$11.80
Purchase #5	$208.90	6.567%	$222.6185	$222.62	$222.60	$222.60
Purchase #6	$75.83	9.386%	$82.9474	$82.95	$82.95	$82.90
Purchase #7	$141.56	11.350%	$157.6271	$157.63	$157.65	$157.60
7 purchase totals =	$703.53		$758.5784	$758.59	$758.60	$758.40