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	$54.47	13.513%	$61.8305	$61.83	$61.85	$61.80
Purchase #2	$25.54	13.107%	$28.8875	$28.89	$28.90	$28.90
Purchase #3	$74.61	11.705%	$83.3431	$83.34	$83.35	$83.30
Purchase #4	$29.81	10.760%	$33.0176	$33.02	$33.00	$33.00
Purchase #5	$184.45	13.624%	$209.5795	$209.58	$209.60	$209.60
Purchase #6	$158.93	6.310%	$168.9585	$168.96	$168.95	$169.00
Purchase #7	$136.29	4.747%	$142.7597	$142.76	$142.75	$142.80
7 purchase totals =	$664.10		$728.3764	$728.38	$728.40	$728.40