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	$111.32	13.384%	$126.2191	$126.22	$126.20	$126.20
Purchase #2	$90.42	9.259%	$98.792	$98.79	$98.80	$98.80
Purchase #3	$176.99	8.376%	$191.8147	$191.81	$191.80	$191.80
Purchase #4	$96.50	4.383%	$100.7296	$100.73	$100.75	$100.70
Purchase #5	$65.42	8.767%	$71.1554	$71.16	$71.15	$71.20
Purchase #6	$94.84	11.285%	$105.5427	$105.54	$105.55	$105.50
Purchase #7	$164.42	9.630%	$180.2536	$180.25	$180.25	$180.30
7 purchase totals =	$799.91		$874.5071	$874.50	$874.50	$874.50