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	$44.27	5.707%	$46.7965	$46.80	$46.80	$46.80
Purchase #2	$25.47	9.487%	$27.8863	$27.89	$27.90	$27.90
Purchase #3	$216.58	6.786%	$231.2771	$231.28	$231.30	$231.30
Purchase #4	$63.38	12.760%	$71.4673	$71.47	$71.45	$71.50
Purchase #5	$139.31	11.469%	$155.2875	$155.29	$155.30	$155.30
Purchase #6	$89.63	5.518%	$94.5758	$94.58	$94.60	$94.60
Purchase #7	$239.41	13.299%	$271.2491	$271.25	$271.25	$271.20
7 purchase totals =	$818.05		$898.5396	$898.56	$898.60	$898.60