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	$232.93	4.694%	$243.8637	$243.86	$243.85	$243.90
Purchase #2	$217.74	12.825%	$245.6652	$245.67	$245.65	$245.70
Purchase #3	$154.89	6.845%	$165.4922	$165.49	$165.50	$165.50
Purchase #4	$201.31	7.461%	$216.3297	$216.33	$216.35	$216.30
Purchase #5	$70.54	13.639%	$80.161	$80.16	$80.15	$80.20
Purchase #6	$207.97	12.278%	$233.5046	$233.50	$233.50	$233.50
Purchase #7	$89.87	11.564%	$100.2626	$100.26	$100.25	$100.30
7 purchase totals =	$1,175.25		$1,285.2790	$1,285.27	$1,285.25	$1,285.40