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	$139.63	9.403%	$152.7594	$152.76	$152.75	$152.80
Purchase #2	$55.58	4.310%	$57.9755	$57.98	$58.00	$58.00
Purchase #3	$81.89	11.629%	$91.413	$91.41	$91.40	$91.40
Purchase #4	$76.67	11.555%	$85.5292	$85.53	$85.55	$85.50
Purchase #5	$199.96	4.635%	$209.2281	$209.23	$209.25	$209.20
Purchase #6	$75.75	10.630%	$83.8022	$83.80	$83.80	$83.80
Purchase #7	$65.46	11.134%	$72.7483	$72.75	$72.75	$72.70
7 purchase totals =	$694.94		$753.4557	$753.46	$753.50	$753.40