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	$82.31	10.475%	$90.932	$90.93	$90.95	$90.90
Purchase #2	$125.47	10.818%	$139.0433	$139.04	$139.05	$139.00
Purchase #3	$136.83	9.869%	$150.3338	$150.33	$150.35	$150.30
Purchase #4	$166.77	3.411%	$172.4585	$172.46	$172.45	$172.50
Purchase #5	$83.72	11.664%	$93.4851	$93.49	$93.50	$93.50
Purchase #6	$172.80	4.378%	$180.3652	$180.37	$180.35	$180.40
Purchase #7	$109.25	11.116%	$121.3942	$121.39	$121.40	$121.40
7 purchase totals =	$877.15		$948.0121	$948.01	$948.05	$948.00