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	$115.32	8.141%	$124.7082	$124.71	$124.70	$124.70
Purchase #2	$19.34	3.162%	$19.9515	$19.95	$19.95	$20.00
Purchase #3	$223.59	8.843%	$243.3621	$243.36	$243.35	$243.40
Purchase #4	$220.41	3.862%	$228.9222	$228.92	$228.90	$228.90
Purchase #5	$63.74	13.412%	$72.2888	$72.29	$72.30	$72.30
Purchase #6	$27.55	4.768%	$28.8636	$28.86	$28.85	$28.90
Purchase #7	$40.83	6.484%	$43.4774	$43.48	$43.50	$43.50
7 purchase totals =	$710.78		$761.5738	$761.57	$761.55	$761.70