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	$115.27	6.541%	$122.8098	$122.81	$122.80	$122.80
Purchase #2	$54.52	10.185%	$60.0729	$60.07	$60.05	$60.10
Purchase #3	$164.98	13.449%	$187.1682	$187.17	$187.15	$187.20
Purchase #4	$101.71	3.745%	$105.519	$105.52	$105.50	$105.50
Purchase #5	$131.37	7.614%	$141.3725	$141.37	$141.35	$141.40
Purchase #6	$238.65	7.489%	$256.5225	$256.52	$256.50	$256.50
Purchase #7	$206.81	6.872%	$221.022	$221.02	$221.00	$221.00
7 purchase totals =	$1,013.31		$1,094.4869	$1,094.48	$1,094.35	$1,094.50