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	$243.53	4.232%	$253.8362	$253.84	$253.85	$253.80
Purchase #2	$203.51	5.285%	$214.2655	$214.27	$214.25	$214.30
Purchase #3	$215.68	7.403%	$231.6468	$231.65	$231.65	$231.60
Purchase #4	$93.87	11.486%	$104.6519	$104.65	$104.65	$104.70
Purchase #5	$185.44	11.537%	$206.8342	$206.83	$206.85	$206.80
Purchase #6	$43.28	4.285%	$45.1345	$45.13	$45.15	$45.10
Purchase #7	$51.29	6.698%	$54.7254	$54.73	$54.75	$54.70
7 purchase totals =	$1,036.60		$1,111.0945	$1,111.10	$1,111.15	$1,111.00