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	$50.75	11.471%	$56.5715	$56.57	$56.55	$56.60
Purchase #2	$216.67	8.107%	$234.2354	$234.24	$234.25	$234.20
Purchase #3	$83.66	6.588%	$89.1715	$89.17	$89.15	$89.20
Purchase #4	$220.33	11.344%	$245.3242	$245.32	$245.30	$245.30
Purchase #5	$243.64	3.486%	$252.1333	$252.13	$252.15	$252.10
Purchase #6	$175.87	3.867%	$182.6709	$182.67	$182.65	$182.70
Purchase #7	$175.71	11.759%	$196.3717	$196.37	$196.35	$196.40
7 purchase totals =	$1,166.63		$1,256.4785	$1,256.47	$1,256.40	$1,256.50