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	$81.93	4.158%	$85.3366	$85.34	$85.35	$85.30
Purchase #2	$183.92	8.560%	$199.6636	$199.66	$199.65	$199.70
Purchase #3	$153.63	11.144%	$170.7505	$170.75	$170.75	$170.80
Purchase #4	$109.68	8.341%	$118.8284	$118.83	$118.85	$118.80
Purchase #5	$161.42	4.799%	$169.1665	$169.17	$169.15	$169.20
Purchase #6	$94.80	6.865%	$101.308	$101.31	$101.30	$101.30
Purchase #7	$211.54	5.152%	$222.4385	$222.44	$222.45	$222.40
7 purchase totals =	$996.92		$1,067.4921	$1,067.50	$1,067.50	$1,067.50