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	$49.38	5.635%	$52.1626	$52.16	$52.15	$52.20
Purchase #2	$31.79	6.396%	$33.8233	$33.82	$33.80	$33.80
Purchase #3	$64.51	3.811%	$66.9685	$66.97	$66.95	$67.00
Purchase #4	$202.33	4.679%	$211.797	$211.80	$211.80	$211.80
Purchase #5	$43.73	4.370%	$45.641	$45.64	$45.65	$45.60
Purchase #6	$35.72	12.222%	$40.0857	$40.09	$40.10	$40.10
Purchase #7	$242.45	4.720%	$253.8936	$253.89	$253.90	$253.90
7 purchase totals =	$669.91		$704.3717	$704.37	$704.35	$704.40