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	$205.74	7.120%	$220.3887	$220.39	$220.40	$220.40
Purchase #2	$81.90	9.420%	$89.615	$89.62	$89.60	$89.60
Purchase #3	$193.67	13.499%	$219.8135	$219.81	$219.80	$219.80
Purchase #4	$116.49	12.541%	$131.099	$131.10	$131.10	$131.10
Purchase #5	$219.95	8.446%	$238.527	$238.53	$238.55	$238.50
Purchase #6	$36.87	7.864%	$39.7695	$39.77	$39.75	$39.80
Purchase #7	$137.91	6.190%	$146.4466	$146.45	$146.45	$146.40
7 purchase totals =	$992.53		$1,085.6593	$1,085.67	$1,085.65	$1,085.60