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	$209.87	4.326%	$218.949	$218.95	$218.95	$218.90
Purchase #2	$180.53	6.498%	$192.2608	$192.26	$192.25	$192.30
Purchase #3	$165.73	4.588%	$173.3337	$173.33	$173.35	$173.30
Purchase #4	$142.46	9.594%	$156.1276	$156.13	$156.15	$156.10
Purchase #5	$176.68	11.508%	$197.0123	$197.01	$197.00	$197.00
Purchase #6	$54.72	8.745%	$59.5053	$59.51	$59.50	$59.50
Purchase #7	$19.53	6.404%	$20.7807	$20.78	$20.80	$20.80
7 purchase totals =	$949.52		$1,017.9694	$1,017.97	$1,018.00	$1,017.90