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	$128.63	12.435%	$144.6251	$144.63	$144.65	$144.60
Purchase #2	$122.90	7.312%	$131.8864	$131.89	$131.90	$131.90
Purchase #3	$47.80	12.629%	$53.8367	$53.84	$53.85	$53.80
Purchase #4	$31.51	11.735%	$35.2077	$35.21	$35.20	$35.20
Purchase #5	$99.35	3.664%	$102.9902	$102.99	$103.00	$103.00
Purchase #6	$115.66	13.415%	$131.1758	$131.18	$131.20	$131.20
Purchase #7	$180.67	8.672%	$196.3377	$196.34	$196.35	$196.30
7 purchase totals =	$726.52		$796.0596	$796.08	$796.15	$796.00