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	$213.47	5.165%	$224.4957	$224.50	$224.50	$224.50
Purchase #2	$118.52	5.238%	$124.7281	$124.73	$124.75	$124.70
Purchase #3	$221.95	10.435%	$245.1105	$245.11	$245.10	$245.10
Purchase #4	$43.30	5.114%	$45.5144	$45.51	$45.50	$45.50
Purchase #5	$219.91	8.402%	$238.3868	$238.39	$238.40	$238.40
Purchase #6	$167.70	11.831%	$187.5406	$187.54	$187.55	$187.50
Purchase #7	$211.93	11.244%	$235.7594	$235.76	$235.75	$235.80
7 purchase totals =	$1,196.78		$1,301.5355	$1,301.54	$1,301.55	$1,301.50