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	$40.86	13.788%	$46.4938	$46.49	$46.50	$46.50
Purchase #2	$165.56	12.787%	$186.7302	$186.73	$186.75	$186.70
Purchase #3	$35.90	10.698%	$39.7406	$39.74	$39.75	$39.70
Purchase #4	$191.97	7.636%	$206.6288	$206.63	$206.65	$206.60
Purchase #5	$73.66	11.590%	$82.1972	$82.20	$82.20	$82.20
Purchase #6	$39.42	4.753%	$41.2936	$41.29	$41.30	$41.30
Purchase #7	$134.80	11.651%	$150.5055	$150.51	$150.50	$150.50
7 purchase totals =	$682.17		$753.5897	$753.59	$753.65	$753.50