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	$118.45	3.220%	$122.2641	$122.26	$122.25	$122.30
Purchase #2	$71.73	9.113%	$78.2668	$78.27	$78.25	$78.30
Purchase #3	$179.66	9.633%	$196.9666	$196.97	$196.95	$197.00
Purchase #4	$192.86	12.193%	$216.3754	$216.38	$216.40	$216.40
Purchase #5	$153.46	4.131%	$159.7994	$159.80	$159.80	$159.80
Purchase #6	$119.35	11.831%	$133.4703	$133.47	$133.45	$133.50
Purchase #7	$90.67	10.459%	$100.1532	$100.15	$100.15	$100.20
7 purchase totals =	$926.18		$1,007.2958	$1,007.30	$1,007.25	$1,007.50