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	$233.41	13.489%	$264.8947	$264.89	$264.90	$264.90
Purchase #2	$200.32	13.460%	$227.2831	$227.28	$227.30	$227.30
Purchase #3	$171.71	13.675%	$195.1913	$195.19	$195.20	$195.20
Purchase #4	$47.36	7.734%	$51.0228	$51.02	$51.00	$51.00
Purchase #5	$33.76	10.592%	$37.3359	$37.34	$37.35	$37.30
Purchase #6	$139.38	4.363%	$145.4611	$145.46	$145.45	$145.50
Purchase #7	$19.54	5.217%	$20.5594	$20.56	$20.55	$20.60
7 purchase totals =	$845.48		$941.7483	$941.74	$941.75	$941.80