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	$67.25	6.593%	$71.6838	$71.68	$71.70	$71.70
Purchase #2	$82.56	9.737%	$90.5989	$90.60	$90.60	$90.60
Purchase #3	$186.52	4.494%	$194.9022	$194.90	$194.90	$194.90
Purchase #4	$151.72	8.567%	$164.7179	$164.72	$164.70	$164.70
Purchase #5	$242.90	9.285%	$265.4533	$265.45	$265.45	$265.50
Purchase #6	$194.87	5.155%	$204.9155	$204.92	$204.90	$204.90
Purchase #7	$131.55	11.740%	$146.994	$146.99	$147.00	$147.00
7 purchase totals =	$1,057.37		$1,139.2656	$1,139.26	$1,139.25	$1,139.30