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	$219.31	12.675%	$247.1075	$247.11	$247.10	$247.10
Purchase #2	$241.49	5.856%	$255.6317	$255.63	$255.65	$255.60
Purchase #3	$42.63	12.615%	$48.0078	$48.01	$48.00	$48.00
Purchase #4	$17.40	3.800%	$18.0612	$18.06	$18.05	$18.10
Purchase #5	$55.83	6.760%	$59.6041	$59.60	$59.60	$59.60
Purchase #6	$126.26	6.212%	$134.1033	$134.10	$134.10	$134.10
Purchase #7	$125.69	4.109%	$130.8546	$130.85	$130.85	$130.90
7 purchase totals =	$828.61		$893.3702	$893.36	$893.35	$893.40