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	$248.45	8.316%	$269.1111	$269.11	$269.10	$269.10
Purchase #2	$163.49	13.632%	$185.777	$185.78	$185.80	$185.80
Purchase #3	$143.90	11.841%	$160.9392	$160.94	$160.95	$160.90
Purchase #4	$231.37	13.384%	$262.3366	$262.34	$262.35	$262.30
Purchase #5	$46.28	4.742%	$48.4746	$48.47	$48.45	$48.50
Purchase #6	$147.38	11.712%	$164.6411	$164.64	$164.65	$164.60
Purchase #7	$130.31	10.247%	$143.6629	$143.66	$143.65	$143.70
7 purchase totals =	$1,111.18		$1,234.9425	$1,234.94	$1,234.95	$1,234.90