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	$204.93	10.166%	$225.7632	$225.76	$225.75	$225.80
Purchase #2	$89.63	11.745%	$100.157	$100.16	$100.15	$100.20
Purchase #3	$164.66	11.559%	$183.693	$183.69	$183.70	$183.70
Purchase #4	$33.63	6.453%	$35.8001	$35.80	$35.80	$35.80
Purchase #5	$37.37	7.704%	$40.249	$40.25	$40.25	$40.20
Purchase #6	$26.27	11.467%	$29.2824	$29.28	$29.30	$29.30
Purchase #7	$172.39	12.789%	$194.437	$194.44	$194.45	$194.40
7 purchase totals =	$728.88		$809.3817	$809.38	$809.40	$809.40