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	$136.85	4.693%	$143.2724	$143.27	$143.25	$143.30
Purchase #2	$131.75	11.717%	$147.1871	$147.19	$147.20	$147.20
Purchase #3	$142.96	7.334%	$153.4447	$153.44	$153.45	$153.40
Purchase #4	$185.71	5.706%	$196.3066	$196.31	$196.30	$196.30
Purchase #5	$129.67	12.105%	$145.3666	$145.37	$145.35	$145.40
Purchase #6	$77.47	12.628%	$87.2529	$87.25	$87.25	$87.30
Purchase #7	$144.62	12.295%	$162.401	$162.40	$162.40	$162.40
7 purchase totals =	$949.03		$1,035.2313	$1,035.23	$1,035.20	$1,035.30