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	$191.48	12.663%	$215.7271	$215.73	$215.75	$215.70
Purchase #2	$40.44	13.465%	$45.8852	$45.89	$45.90	$45.90
Purchase #3	$169.64	3.784%	$176.0592	$176.06	$176.05	$176.10
Purchase #4	$11.48	8.495%	$12.4552	$12.46	$12.45	$12.50
Purchase #5	$214.49	12.801%	$241.9469	$241.95	$241.95	$241.90
Purchase #6	$209.90	4.570%	$219.4924	$219.49	$219.50	$219.50
Purchase #7	$234.54	10.112%	$258.2567	$258.26	$258.25	$258.30
7 purchase totals =	$1,071.97		$1,169.8227	$1,169.84	$1,169.85	$1,169.90