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	$160.28	7.154%	$171.7464	$171.75	$171.75	$171.70
Purchase #2	$27.66	6.647%	$29.4986	$29.50	$29.50	$29.50
Purchase #3	$162.63	11.166%	$180.7893	$180.79	$180.80	$180.80
Purchase #4	$89.44	11.745%	$99.9447	$99.94	$99.95	$99.90
Purchase #5	$226.82	11.761%	$253.4963	$253.50	$253.50	$253.50
Purchase #6	$242.80	13.811%	$276.3331	$276.33	$276.35	$276.30
Purchase #7	$134.75	3.774%	$139.8355	$139.84	$139.85	$139.80
7 purchase totals =	$1,044.38		$1,151.6439	$1,151.65	$1,151.70	$1,151.50