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	$93.67	11.475%	$104.4186	$104.42	$104.40	$104.40
Purchase #2	$197.98	3.397%	$204.7054	$204.71	$204.70	$204.70
Purchase #3	$78.78	4.572%	$82.3818	$82.38	$82.40	$82.40
Purchase #4	$79.37	12.837%	$89.5587	$89.56	$89.55	$89.60
Purchase #5	$170.83	13.633%	$194.1193	$194.12	$194.10	$194.10
Purchase #6	$139.59	5.433%	$147.1739	$147.17	$147.15	$147.20
Purchase #7	$104.95	6.817%	$112.1044	$112.10	$112.10	$112.10
7 purchase totals =	$865.17		$934.4621	$934.46	$934.40	$934.50