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	$40.95	11.693%	$45.7383	$45.74	$45.75	$45.70
Purchase #2	$56.46	6.130%	$59.921	$59.92	$59.90	$59.90
Purchase #3	$92.95	5.840%	$98.3783	$98.38	$98.40	$98.40
Purchase #4	$50.47	6.635%	$53.8187	$53.82	$53.80	$53.80
Purchase #5	$177.91	11.117%	$197.6883	$197.69	$197.70	$197.70
Purchase #6	$97.57	5.558%	$102.9929	$102.99	$103.00	$103.00
Purchase #7	$47.89	13.677%	$54.4399	$54.44	$54.45	$54.40
7 purchase totals =	$564.20		$612.9774	$612.98	$613.00	$612.90