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	$52.73	9.358%	$57.6645	$57.66	$57.65	$57.70
Purchase #2	$130.79	10.506%	$144.5308	$144.53	$144.55	$144.50
Purchase #3	$64.80	8.722%	$70.4519	$70.45	$70.45	$70.50
Purchase #4	$123.79	6.462%	$131.7893	$131.79	$131.80	$131.80
Purchase #5	$191.86	9.167%	$209.4478	$209.45	$209.45	$209.40
Purchase #6	$241.71	3.717%	$250.6944	$250.69	$250.70	$250.70
Purchase #7	$153.83	3.856%	$159.7617	$159.76	$159.75	$159.80
7 purchase totals =	$959.51		$1,024.3404	$1,024.33	$1,024.35	$1,024.40