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	$210.53	8.139%	$227.665	$227.67	$227.65	$227.70
Purchase #2	$123.30	10.556%	$136.3155	$136.32	$136.30	$136.30
Purchase #3	$228.82	4.293%	$238.6432	$238.64	$238.65	$238.60
Purchase #4	$22.95	5.199%	$24.1432	$24.14	$24.15	$24.10
Purchase #5	$167.82	10.721%	$185.812	$185.81	$185.80	$185.80
Purchase #6	$55.73	10.398%	$61.5248	$61.52	$61.50	$61.50
Purchase #7	$126.43	9.662%	$138.6457	$138.65	$138.65	$138.60
7 purchase totals =	$935.58		$1,012.7494	$1,012.75	$1,012.70	$1,012.60