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	$104.28	7.167%	$111.7537	$111.75	$111.75	$111.80
Purchase #2	$235.83	10.208%	$259.9035	$259.90	$259.90	$259.90
Purchase #3	$186.39	8.761%	$202.7196	$202.72	$202.70	$202.70
Purchase #4	$112.43	11.649%	$125.527	$125.53	$125.55	$125.50
Purchase #5	$110.48	7.169%	$118.4003	$118.40	$118.40	$118.40
Purchase #6	$175.68	5.782%	$185.8378	$185.84	$185.85	$185.80
Purchase #7	$33.50	10.760%	$37.1046	$37.10	$37.10	$37.10
7 purchase totals =	$958.59		$1,041.2465	$1,041.24	$1,041.25	$1,041.20