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	$209.94	6.340%	$223.2502	$223.25	$223.25	$223.30
Purchase #2	$206.62	7.497%	$222.1103	$222.11	$222.10	$222.10
Purchase #3	$69.54	13.169%	$78.6977	$78.70	$78.70	$78.70
Purchase #4	$8.58	12.434%	$9.6468	$9.65	$9.65	$9.60
Purchase #5	$195.50	10.535%	$216.0959	$216.10	$216.10	$216.10
Purchase #6	$54.75	12.846%	$61.7832	$61.78	$61.80	$61.80
Purchase #7	$91.79	12.252%	$103.0361	$103.04	$103.05	$103.00
7 purchase totals =	$836.72		$914.6202	$914.63	$914.65	$914.60