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	$215.32	7.181%	$230.7821	$230.78	$230.80	$230.80
Purchase #2	$172.80	6.863%	$184.6593	$184.66	$184.65	$184.70
Purchase #3	$27.43	4.647%	$28.7047	$28.70	$28.70	$28.70
Purchase #4	$112.96	4.708%	$118.2782	$118.28	$118.30	$118.30
Purchase #5	$91.82	9.512%	$100.5539	$100.55	$100.55	$100.60
Purchase #6	$50.39	4.561%	$52.6883	$52.69	$52.70	$52.70
Purchase #7	$96.34	4.106%	$100.2957	$100.30	$100.30	$100.30
7 purchase totals =	$767.06		$815.9622	$815.96	$816.00	$816.10