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	$69.37	4.654%	$72.5985	$72.60	$72.60	$72.60
Purchase #2	$86.83	5.697%	$91.7767	$91.78	$91.80	$91.80
Purchase #3	$52.52	12.692%	$59.1858	$59.19	$59.20	$59.20
Purchase #4	$236.42	7.819%	$254.9057	$254.91	$254.90	$254.90
Purchase #5	$147.71	8.395%	$160.1103	$160.11	$160.10	$160.10
Purchase #6	$175.82	7.256%	$188.5775	$188.58	$188.60	$188.60
Purchase #7	$90.79	7.541%	$97.6365	$97.64	$97.65	$97.60
7 purchase totals =	$859.46		$924.7910	$924.81	$924.85	$924.80