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	$100.34	4.793%	$105.1493	$105.15	$105.15	$105.10
Purchase #2	$231.76	6.333%	$246.4374	$246.44	$246.45	$246.40
Purchase #3	$114.37	3.774%	$118.6863	$118.69	$118.70	$118.70
Purchase #4	$63.52	4.266%	$66.2298	$66.23	$66.25	$66.20
Purchase #5	$243.67	8.465%	$264.2967	$264.30	$264.30	$264.30
Purchase #6	$130.88	6.274%	$139.0914	$139.09	$139.10	$139.10
Purchase #7	$9.25	13.791%	$10.5257	$10.53	$10.55	$10.50
7 purchase totals =	$893.79		$950.4166	$950.43	$950.50	$950.30