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	$93.96	9.702%	$103.076	$103.08	$103.10	$103.10
Purchase #2	$226.52	7.662%	$243.876	$243.88	$243.90	$243.90
Purchase #3	$98.85	6.154%	$104.9332	$104.93	$104.95	$104.90
Purchase #4	$215.94	3.540%	$223.5843	$223.58	$223.60	$223.60
Purchase #5	$34.57	9.613%	$37.8932	$37.89	$37.90	$37.90
Purchase #6	$208.43	9.335%	$227.8869	$227.89	$227.90	$227.90
Purchase #7	$72.79	9.390%	$79.625	$79.63	$79.65	$79.60
7 purchase totals =	$951.06		$1,020.8746	$1,020.88	$1,021.00	$1,020.90