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	$248.84	7.633%	$267.834	$267.83	$267.85	$267.80
Purchase #2	$154.77	12.735%	$174.48	$174.48	$174.50	$174.50
Purchase #3	$152.59	13.323%	$172.9196	$172.92	$172.90	$172.90
Purchase #4	$96.64	12.296%	$108.5229	$108.52	$108.50	$108.50
Purchase #5	$243.45	12.510%	$273.9056	$273.91	$273.90	$273.90
Purchase #6	$33.78	8.334%	$36.5952	$36.60	$36.60	$36.60
Purchase #7	$27.58	11.516%	$30.7561	$30.76	$30.75	$30.80
7 purchase totals =	$957.65		$1,065.0134	$1,065.02	$1,065.00	$1,065.00