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	$51.39	3.473%	$53.1748	$53.17	$53.15	$53.20
Purchase #2	$66.66	5.397%	$70.2576	$70.26	$70.25	$70.30
Purchase #3	$196.59	8.204%	$212.7182	$212.72	$212.70	$212.70
Purchase #4	$57.33	6.166%	$60.865	$60.87	$60.85	$60.90
Purchase #5	$222.82	12.395%	$250.4385	$250.44	$250.45	$250.40
Purchase #6	$235.38	11.822%	$263.2066	$263.21	$263.20	$263.20
Purchase #7	$95.66	10.270%	$105.4843	$105.48	$105.50	$105.50
7 purchase totals =	$925.83		$1,016.1450	$1,016.15	$1,016.10	$1,016.20