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	$115.81	7.555%	$124.5594	$124.56	$124.55	$124.60
Purchase #2	$216.91	3.868%	$225.3001	$225.30	$225.30	$225.30
Purchase #3	$249.50	10.126%	$274.7644	$274.76	$274.75	$274.80
Purchase #4	$133.64	5.155%	$140.5291	$140.53	$140.55	$140.50
Purchase #5	$47.34	9.642%	$51.9045	$51.90	$51.90	$51.90
Purchase #6	$95.50	4.548%	$99.8433	$99.84	$99.85	$99.80
Purchase #7	$235.58	6.510%	$250.9163	$250.92	$250.90	$250.90
7 purchase totals =	$1,094.28		$1,167.8171	$1,167.81	$1,167.80	$1,167.80