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	$191.52	12.628%	$215.7051	$215.71	$215.70	$215.70
Purchase #2	$108.69	6.812%	$116.094	$116.09	$116.10	$116.10
Purchase #3	$85.92	5.127%	$90.3251	$90.33	$90.35	$90.30
Purchase #4	$248.31	7.720%	$267.4795	$267.48	$267.50	$267.50
Purchase #5	$29.34	3.807%	$30.457	$30.46	$30.45	$30.50
Purchase #6	$116.66	11.367%	$129.9207	$129.92	$129.90	$129.90
Purchase #7	$233.58	4.155%	$243.2852	$243.29	$243.30	$243.30
7 purchase totals =	$1,014.02		$1,093.2666	$1,093.28	$1,093.30	$1,093.30