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	$197.90	9.335%	$216.374	$216.37	$216.35	$216.40
Purchase #2	$131.68	6.215%	$139.8639	$139.86	$139.85	$139.90
Purchase #3	$98.92	5.179%	$104.0431	$104.04	$104.05	$104.00
Purchase #4	$234.79	13.113%	$265.578	$265.58	$265.60	$265.60
Purchase #5	$27.67	12.141%	$31.0294	$31.03	$31.05	$31.00
Purchase #6	$205.45	13.866%	$233.9377	$233.94	$233.95	$233.90
Purchase #7	$105.42	11.399%	$117.4368	$117.44	$117.45	$117.40
7 purchase totals =	$1,001.83		$1,108.2629	$1,108.26	$1,108.30	$1,108.20