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	$237.34	7.314%	$254.699	$254.70	$254.70	$254.70
Purchase #2	$30.66	9.219%	$33.4865	$33.49	$33.50	$33.50
Purchase #3	$231.29	5.280%	$243.5021	$243.50	$243.50	$243.50
Purchase #4	$95.25	5.281%	$100.2802	$100.28	$100.30	$100.30
Purchase #5	$9.32	7.283%	$9.9988	$10.00	$10.00	$10.00
Purchase #6	$147.48	10.446%	$162.8858	$162.89	$162.90	$162.90
Purchase #7	$135.90	12.127%	$152.3806	$152.38	$152.40	$152.40
7 purchase totals =	$887.24		$957.2330	$957.24	$957.30	$957.30