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	$158.32	6.496%	$168.6045	$168.60	$168.60	$168.60
Purchase #2	$232.51	6.508%	$247.6418	$247.64	$247.65	$247.60
Purchase #3	$57.42	3.258%	$59.2907	$59.29	$59.30	$59.30
Purchase #4	$99.86	7.527%	$107.3765	$107.38	$107.40	$107.40
Purchase #5	$222.84	11.230%	$247.8649	$247.86	$247.85	$247.90
Purchase #6	$15.41	13.179%	$17.4409	$17.44	$17.45	$17.40
Purchase #7	$140.28	11.436%	$156.3224	$156.32	$156.30	$156.30
7 purchase totals =	$926.64		$1,004.5417	$1,004.53	$1,004.55	$1,004.50