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	$93.37	10.552%	$103.2224	$103.22	$103.20	$103.20
Purchase #2	$25.92	10.229%	$28.5714	$28.57	$28.55	$28.60
Purchase #3	$59.60	4.510%	$62.288	$62.29	$62.30	$62.30
Purchase #4	$41.76	9.528%	$45.7389	$45.74	$45.75	$45.70
Purchase #5	$11.54	3.127%	$11.9009	$11.90	$11.90	$11.90
Purchase #6	$20.32	8.827%	$22.1136	$22.11	$22.10	$22.10
Purchase #7	$13.60	7.659%	$14.6416	$14.64	$14.65	$14.60
7 purchase totals =	$266.11		$288.4768	$288.47	$288.45	$288.40