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	$130.43	11.724%	$145.7216	$145.72	$145.70	$145.70
Purchase #2	$35.82	5.820%	$37.9047	$37.90	$37.90	$37.90
Purchase #3	$189.48	3.610%	$196.3202	$196.32	$196.30	$196.30
Purchase #4	$40.46	4.770%	$42.3899	$42.39	$42.40	$42.40
Purchase #5	$63.80	3.715%	$66.1702	$66.17	$66.15	$66.20
Purchase #6	$137.48	11.393%	$153.1431	$153.14	$153.15	$153.10
Purchase #7	$6.74	3.156%	$6.9527	$6.95	$6.95	$7.00
7 purchase totals =	$604.21		$648.6024	$648.59	$648.55	$648.60