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	$242.72	3.190%	$250.4628	$250.46	$250.45	$250.50
Purchase #2	$39.28	8.264%	$42.5261	$42.53	$42.55	$42.50
Purchase #3	$242.69	4.777%	$254.2833	$254.28	$254.30	$254.30
Purchase #4	$124.85	6.144%	$132.5208	$132.52	$132.50	$132.50
Purchase #5	$148.69	13.311%	$168.4821	$168.48	$168.50	$168.50
Purchase #6	$216.61	3.462%	$224.109	$224.11	$224.10	$224.10
Purchase #7	$137.88	12.557%	$155.1936	$155.19	$155.20	$155.20
7 purchase totals =	$1,152.72		$1,227.5777	$1,227.57	$1,227.60	$1,227.60