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	$6.93	8.519%	$7.5204	$7.52	$7.50	$7.50
Purchase #2	$63.47	5.388%	$66.8898	$66.89	$66.90	$66.90
Purchase #3	$238.55	8.779%	$259.4923	$259.49	$259.50	$259.50
Purchase #4	$230.84	7.340%	$247.7837	$247.78	$247.80	$247.80
Purchase #5	$170.94	4.324%	$178.3314	$178.33	$178.35	$178.30
Purchase #6	$78.36	10.180%	$86.337	$86.34	$86.35	$86.30
Purchase #7	$183.38	9.229%	$200.3041	$200.30	$200.30	$200.30
7 purchase totals =	$972.47		$1,046.6587	$1,046.65	$1,046.70	$1,046.60