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	$42.49	11.760%	$47.4868	$47.49	$47.50	$47.50
Purchase #2	$217.47	3.546%	$225.1815	$225.18	$225.20	$225.20
Purchase #3	$69.86	12.530%	$78.6135	$78.61	$78.60	$78.60
Purchase #4	$248.50	13.358%	$281.6946	$281.69	$281.70	$281.70
Purchase #5	$181.59	12.642%	$204.5466	$204.55	$204.55	$204.50
Purchase #6	$118.25	6.749%	$126.2307	$126.23	$126.25	$126.20
Purchase #7	$45.31	7.554%	$48.7327	$48.73	$48.75	$48.70
7 purchase totals =	$923.47		$1,012.4864	$1,012.48	$1,012.55	$1,012.40