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	$143.37	11.685%	$160.1228	$160.12	$160.10	$160.10
Purchase #2	$96.33	4.268%	$100.4414	$100.44	$100.45	$100.40
Purchase #3	$12.55	11.494%	$13.9925	$13.99	$14.00	$14.00
Purchase #4	$241.88	13.805%	$275.2715	$275.27	$275.25	$275.30
Purchase #5	$30.82	10.122%	$33.9396	$33.94	$33.95	$33.90
Purchase #6	$194.74	13.643%	$221.3084	$221.31	$221.30	$221.30
Purchase #7	$227.82	3.518%	$235.8347	$235.83	$235.85	$235.80
7 purchase totals =	$947.51		$1,040.9109	$1,040.90	$1,040.90	$1,040.80