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	$170.31	7.170%	$182.5212	$182.52	$182.50	$182.50
Purchase #2	$35.72	4.423%	$37.2999	$37.30	$37.30	$37.30
Purchase #3	$23.92	5.821%	$25.3124	$25.31	$25.30	$25.30
Purchase #4	$219.44	6.798%	$234.3575	$234.36	$234.35	$234.40
Purchase #5	$243.69	4.274%	$254.1053	$254.11	$254.10	$254.10
Purchase #6	$41.32	3.744%	$42.867	$42.87	$42.85	$42.90
Purchase #7	$164.92	11.200%	$183.391	$183.39	$183.40	$183.40
7 purchase totals =	$899.32		$959.8543	$959.86	$959.80	$959.90