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	$68.38	12.227%	$76.7408	$76.74	$76.75	$76.70
Purchase #2	$164.60	5.464%	$173.5937	$173.59	$173.60	$173.60
Purchase #3	$211.84	3.525%	$219.3074	$219.31	$219.30	$219.30
Purchase #4	$52.85	8.693%	$57.4443	$57.44	$57.45	$57.40
Purchase #5	$58.78	7.391%	$63.1244	$63.12	$63.10	$63.10
Purchase #6	$34.51	7.603%	$37.1338	$37.13	$37.15	$37.10
Purchase #7	$39.90	5.521%	$42.1029	$42.10	$42.10	$42.10
7 purchase totals =	$630.86		$669.4473	$669.43	$669.45	$669.30