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	$94.31	11.208%	$104.8803	$104.88	$104.90	$104.90
Purchase #2	$152.79	12.231%	$171.4777	$171.48	$171.50	$171.50
Purchase #3	$248.76	11.309%	$276.8923	$276.89	$276.90	$276.90
Purchase #4	$72.82	3.542%	$75.3993	$75.40	$75.40	$75.40
Purchase #5	$246.92	3.198%	$254.8165	$254.82	$254.80	$254.80
Purchase #6	$37.49	11.795%	$41.9119	$41.91	$41.90	$41.90
Purchase #7	$114.60	3.307%	$118.3898	$118.39	$118.40	$118.40
7 purchase totals =	$967.69		$1,043.7678	$1,043.77	$1,043.80	$1,043.80