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	$203.49	9.284%	$222.382	$222.38	$222.40	$222.40
Purchase #2	$197.48	7.401%	$212.0955	$212.10	$212.10	$212.10
Purchase #3	$96.70	8.362%	$104.7861	$104.79	$104.80	$104.80
Purchase #4	$65.26	7.313%	$70.0325	$70.03	$70.05	$70.00
Purchase #5	$79.51	13.715%	$90.4148	$90.41	$90.40	$90.40
Purchase #6	$83.87	9.769%	$92.0633	$92.06	$92.05	$92.10
Purchase #7	$50.50	9.864%	$55.4813	$55.48	$55.50	$55.50
7 purchase totals =	$776.81		$847.2555	$847.25	$847.30	$847.30