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	$45.26	13.288%	$51.2741	$51.27	$51.25	$51.30
Purchase #2	$160.26	12.620%	$180.4848	$180.48	$180.50	$180.50
Purchase #3	$83.60	13.672%	$95.0298	$95.03	$95.05	$95.00
Purchase #4	$134.83	6.440%	$143.5131	$143.51	$143.50	$143.50
Purchase #5	$166.33	11.485%	$185.433	$185.43	$185.45	$185.40
Purchase #6	$173.85	8.112%	$187.9527	$187.95	$187.95	$188.00
Purchase #7	$159.56	13.509%	$181.115	$181.12	$181.10	$181.10
7 purchase totals =	$923.69		$1,024.8025	$1,024.79	$1,024.80	$1,024.80