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	$201.83	4.588%	$211.09	$211.09	$211.10	$211.10
Purchase #2	$29.52	9.664%	$32.3728	$32.37	$32.35	$32.40
Purchase #3	$144.71	11.132%	$160.8191	$160.82	$160.80	$160.80
Purchase #4	$116.66	12.850%	$131.6508	$131.65	$131.65	$131.70
Purchase #5	$12.83	12.333%	$14.4123	$14.41	$14.40	$14.40
Purchase #6	$92.96	7.138%	$99.5955	$99.60	$99.60	$99.60
Purchase #7	$24.95	9.588%	$27.3422	$27.34	$27.35	$27.30
7 purchase totals =	$623.46		$677.2827	$677.28	$677.25	$677.30