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	$238.38	12.856%	$269.0261	$269.03	$269.05	$269.00
Purchase #2	$61.45	10.864%	$68.1259	$68.13	$68.15	$68.10
Purchase #3	$180.45	10.502%	$199.4009	$199.40	$199.40	$199.40
Purchase #4	$200.44	5.697%	$211.8591	$211.86	$211.85	$211.90
Purchase #5	$69.72	3.317%	$72.0326	$72.03	$72.05	$72.00
Purchase #6	$72.27	5.775%	$76.4436	$76.44	$76.45	$76.40
Purchase #7	$53.76	3.353%	$55.5626	$55.56	$55.55	$55.60
7 purchase totals =	$876.47		$952.4508	$952.45	$952.50	$952.40