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	$217.25	7.310%	$233.131	$233.13	$233.15	$233.10
Purchase #2	$73.25	11.282%	$81.5141	$81.51	$81.50	$81.50
Purchase #3	$83.90	6.740%	$89.5549	$89.55	$89.55	$89.60
Purchase #4	$175.44	10.810%	$194.4051	$194.41	$194.40	$194.40
Purchase #5	$149.27	13.548%	$169.4931	$169.49	$169.50	$169.50
Purchase #6	$128.47	9.642%	$140.8571	$140.86	$140.85	$140.90
Purchase #7	$107.64	6.702%	$114.854	$114.85	$114.85	$114.90
7 purchase totals =	$935.22		$1,023.8093	$1,023.80	$1,023.80	$1,023.90