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	$156.92	7.644%	$168.915	$168.92	$168.90	$168.90
Purchase #2	$90.67	7.375%	$97.3569	$97.36	$97.35	$97.40
Purchase #3	$158.59	11.222%	$176.387	$176.39	$176.40	$176.40
Purchase #4	$159.95	9.511%	$175.1628	$175.16	$175.15	$175.20
Purchase #5	$47.31	12.838%	$53.3837	$53.38	$53.40	$53.40
Purchase #6	$245.62	10.689%	$271.8743	$271.87	$271.85	$271.90
Purchase #7	$63.39	4.584%	$66.2958	$66.30	$66.30	$66.30
7 purchase totals =	$922.45		$1,009.3755	$1,009.38	$1,009.35	$1,009.50