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	$12.90	13.665%	$14.6628	$14.66	$14.65	$14.70
Purchase #2	$245.80	3.834%	$255.224	$255.22	$255.20	$255.20
Purchase #3	$70.89	6.608%	$75.5744	$75.57	$75.55	$75.60
Purchase #4	$57.33	5.333%	$60.3874	$60.39	$60.40	$60.40
Purchase #5	$178.59	5.334%	$188.116	$188.12	$188.10	$188.10
Purchase #6	$237.52	9.147%	$259.246	$259.25	$259.25	$259.20
Purchase #7	$148.89	11.832%	$166.5067	$166.51	$166.50	$166.50
7 purchase totals =	$951.92		$1,019.7173	$1,019.72	$1,019.65	$1,019.70