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	$135.95	8.340%	$147.2882	$147.29	$147.30	$147.30
Purchase #2	$95.45	8.546%	$103.6072	$103.61	$103.60	$103.60
Purchase #3	$48.61	4.640%	$50.8655	$50.87	$50.85	$50.90
Purchase #4	$57.36	6.495%	$61.0855	$61.09	$61.10	$61.10
Purchase #5	$145.72	4.779%	$152.684	$152.68	$152.70	$152.70
Purchase #6	$65.87	7.654%	$70.9117	$70.91	$70.90	$70.90
Purchase #7	$205.35	8.287%	$222.3674	$222.37	$222.35	$222.40
7 purchase totals =	$754.31		$808.8095	$808.82	$808.80	$808.90