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	$158.82	3.373%	$164.177	$164.18	$164.20	$164.20
Purchase #2	$205.69	11.241%	$228.8116	$228.81	$228.80	$228.80
Purchase #3	$82.33	13.336%	$93.3095	$93.31	$93.30	$93.30
Purchase #4	$227.57	7.424%	$244.4648	$244.46	$244.45	$244.50
Purchase #5	$232.58	12.786%	$262.3177	$262.32	$262.30	$262.30
Purchase #6	$39.73	7.653%	$42.7705	$42.77	$42.75	$42.80
Purchase #7	$121.53	12.626%	$136.8744	$136.87	$136.85	$136.90
7 purchase totals =	$1,068.25		$1,172.7255	$1,172.72	$1,172.65	$1,172.80