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	$64.26	11.128%	$71.4109	$71.41	$71.40	$71.40
Purchase #2	$93.38	7.386%	$100.277	$100.28	$100.30	$100.30
Purchase #3	$102.83	12.619%	$115.8061	$115.81	$115.80	$115.80
Purchase #4	$170.95	8.122%	$184.8346	$184.83	$184.85	$184.80
Purchase #5	$109.67	13.809%	$124.8143	$124.81	$124.80	$124.80
Purchase #6	$168.73	12.702%	$190.1621	$190.16	$190.15	$190.20
Purchase #7	$137.32	11.300%	$152.8372	$152.84	$152.85	$152.80
7 purchase totals =	$847.14		$940.1422	$940.14	$940.15	$940.10