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	$109.69	4.585%	$114.7193	$114.72	$114.70	$114.70
Purchase #2	$46.26	4.393%	$48.2922	$48.29	$48.30	$48.30
Purchase #3	$136.69	7.131%	$146.4374	$146.44	$146.45	$146.40
Purchase #4	$24.39	11.129%	$27.1044	$27.10	$27.10	$27.10
Purchase #5	$121.48	8.411%	$131.6977	$131.70	$131.70	$131.70
Purchase #6	$13.72	11.144%	$15.249	$15.25	$15.25	$15.20
Purchase #7	$80.59	6.301%	$85.668	$85.67	$85.65	$85.70
7 purchase totals =	$532.82		$569.1680	$569.17	$569.15	$569.10