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	$223.42	11.508%	$249.1312	$249.13	$249.15	$249.10
Purchase #2	$40.70	11.114%	$45.2234	$45.22	$45.20	$45.20
Purchase #3	$43.80	5.365%	$46.1499	$46.15	$46.15	$46.10
Purchase #4	$232.50	4.519%	$243.0067	$243.01	$243.00	$243.00
Purchase #5	$149.31	4.551%	$156.1051	$156.11	$156.10	$156.10
Purchase #6	$149.64	10.670%	$165.6066	$165.61	$165.60	$165.60
Purchase #7	$228.34	6.837%	$243.9516	$243.95	$243.95	$244.00
7 purchase totals =	$1,067.71		$1,149.1745	$1,149.18	$1,149.15	$1,149.10