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	$209.45	7.502%	$225.1629	$225.16	$225.15	$225.20
Purchase #2	$45.84	9.566%	$50.2251	$50.23	$50.25	$50.20
Purchase #3	$217.38	11.384%	$242.1265	$242.13	$242.15	$242.10
Purchase #4	$78.66	13.308%	$89.1281	$89.13	$89.15	$89.10
Purchase #5	$179.32	6.408%	$190.8108	$190.81	$190.80	$190.80
Purchase #6	$226.89	7.543%	$244.0043	$244.00	$244.00	$244.00
Purchase #7	$133.82	13.827%	$152.3233	$152.32	$152.30	$152.30
7 purchase totals =	$1,091.36		$1,193.7810	$1,193.78	$1,193.80	$1,193.70