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	$65.89	8.651%	$71.5901	$71.59	$71.60	$71.60
Purchase #2	$118.54	3.649%	$122.8655	$122.87	$122.85	$122.90
Purchase #3	$231.54	5.688%	$244.71	$244.71	$244.70	$244.70
Purchase #4	$179.73	3.450%	$185.9307	$185.93	$185.95	$185.90
Purchase #5	$73.26	12.808%	$82.6431	$82.64	$82.65	$82.60
Purchase #6	$218.81	4.259%	$228.1291	$228.13	$228.15	$228.10
Purchase #7	$209.25	6.306%	$222.4453	$222.45	$222.45	$222.40
7 purchase totals =	$1,097.02		$1,158.3138	$1,158.32	$1,158.35	$1,158.20