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	$184.28	10.193%	$203.0637	$203.06	$203.05	$203.10
Purchase #2	$52.43	10.472%	$57.9205	$57.92	$57.90	$57.90
Purchase #3	$160.40	3.299%	$165.6916	$165.69	$165.70	$165.70
Purchase #4	$30.50	10.559%	$33.7205	$33.72	$33.70	$33.70
Purchase #5	$86.84	4.598%	$90.8329	$90.83	$90.85	$90.80
Purchase #6	$221.87	11.412%	$247.1898	$247.19	$247.20	$247.20
Purchase #7	$245.57	11.651%	$274.1814	$274.18	$274.20	$274.20
7 purchase totals =	$981.89		$1,072.6004	$1,072.59	$1,072.60	$1,072.60