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	$131.99	12.560%	$148.5679	$148.57	$148.55	$148.60
Purchase #2	$84.37	5.627%	$89.1175	$89.12	$89.10	$89.10
Purchase #3	$223.25	13.467%	$253.3151	$253.32	$253.30	$253.30
Purchase #4	$249.58	6.393%	$265.5356	$265.54	$265.55	$265.50
Purchase #5	$248.86	10.367%	$274.6593	$274.66	$274.65	$274.70
Purchase #6	$246.35	11.789%	$275.3922	$275.39	$275.40	$275.40
Purchase #7	$60.32	7.499%	$64.8434	$64.84	$64.85	$64.80
7 purchase totals =	$1,244.72		$1,371.4310	$1,371.44	$1,371.40	$1,371.40