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	$57.68	10.334%	$63.6407	$63.64	$63.65	$63.60
Purchase #2	$39.88	13.806%	$45.3858	$45.39	$45.40	$45.40
Purchase #3	$50.89	12.629%	$57.3169	$57.32	$57.30	$57.30
Purchase #4	$31.91	12.657%	$35.9488	$35.95	$35.95	$35.90
Purchase #5	$89.42	6.565%	$95.2904	$95.29	$95.30	$95.30
Purchase #6	$20.46	10.709%	$22.6511	$22.65	$22.65	$22.70
Purchase #7	$149.62	12.656%	$168.5559	$168.56	$168.55	$168.60
7 purchase totals =	$439.86		$488.7896	$488.80	$488.80	$488.80