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	$156.34	8.144%	$169.0723	$169.07	$169.05	$169.10
Purchase #2	$134.33	4.586%	$140.4904	$140.49	$140.50	$140.50
Purchase #3	$204.90	7.795%	$220.872	$220.87	$220.85	$220.90
Purchase #4	$128.31	9.415%	$140.3904	$140.39	$140.40	$140.40
Purchase #5	$163.76	7.118%	$175.4164	$175.42	$175.40	$175.40
Purchase #6	$50.78	4.632%	$53.1321	$53.13	$53.15	$53.10
Purchase #7	$93.30	13.527%	$105.9207	$105.92	$105.90	$105.90
7 purchase totals =	$931.72		$1,005.2943	$1,005.29	$1,005.25	$1,005.30