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	$122.86	7.278%	$131.8018	$131.80	$131.80	$131.80
Purchase #2	$69.78	5.668%	$73.7351	$73.74	$73.75	$73.70
Purchase #3	$49.31	8.196%	$53.3514	$53.35	$53.35	$53.40
Purchase #4	$18.79	13.779%	$21.3791	$21.38	$21.40	$21.40
Purchase #5	$103.31	7.770%	$111.3372	$111.34	$111.35	$111.30
Purchase #6	$219.35	6.859%	$234.3952	$234.40	$234.40	$234.40
Purchase #7	$65.94	11.253%	$73.3602	$73.36	$73.35	$73.40
7 purchase totals =	$649.34		$699.3600	$699.37	$699.40	$699.40