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	$239.78	10.717%	$265.4772	$265.48	$265.50	$265.50
Purchase #2	$123.57	10.452%	$136.4855	$136.49	$136.50	$136.50
Purchase #3	$46.31	9.529%	$50.7229	$50.72	$50.70	$50.70
Purchase #4	$43.50	13.515%	$49.379	$49.38	$49.40	$49.40
Purchase #5	$247.51	11.228%	$275.3004	$275.30	$275.30	$275.30
Purchase #6	$31.92	10.662%	$35.3233	$35.32	$35.30	$35.30
Purchase #7	$54.30	10.439%	$59.9684	$59.97	$59.95	$60.00
7 purchase totals =	$786.89		$872.6567	$872.66	$872.65	$872.70