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	$81.25	12.349%	$91.2836	$91.28	$91.30	$91.30
Purchase #2	$218.39	10.229%	$240.7291	$240.73	$240.75	$240.70
Purchase #3	$113.28	4.433%	$118.3017	$118.30	$118.30	$118.30
Purchase #4	$18.52	4.552%	$19.363	$19.36	$19.35	$19.40
Purchase #5	$90.29	11.514%	$100.686	$100.69	$100.70	$100.70
Purchase #6	$86.25	4.166%	$89.8432	$89.84	$89.85	$89.80
Purchase #7	$50.89	6.863%	$54.3826	$54.38	$54.40	$54.40
7 purchase totals =	$658.87		$714.5892	$714.58	$714.65	$714.60