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	$109.79	8.693%	$119.334	$119.33	$119.35	$119.30
Purchase #2	$13.92	7.302%	$14.9364	$14.94	$14.95	$14.90
Purchase #3	$146.68	8.341%	$158.9146	$158.91	$158.90	$158.90
Purchase #4	$222.51	13.211%	$251.9058	$251.91	$251.90	$251.90
Purchase #5	$20.34	3.740%	$21.1007	$21.10	$21.10	$21.10
Purchase #6	$181.29	8.369%	$196.4622	$196.46	$196.45	$196.50
Purchase #7	$72.47	8.859%	$78.8901	$78.89	$78.90	$78.90
7 purchase totals =	$767.00		$841.5438	$841.54	$841.55	$841.50