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	$224.95	3.724%	$233.3271	$233.33	$233.35	$233.30
Purchase #2	$247.84	12.288%	$278.2946	$278.29	$278.30	$278.30
Purchase #3	$113.38	12.361%	$127.3949	$127.39	$127.40	$127.40
Purchase #4	$173.27	6.720%	$184.9137	$184.91	$184.90	$184.90
Purchase #5	$227.69	9.373%	$249.0314	$249.03	$249.05	$249.00
Purchase #6	$245.80	4.251%	$256.249	$256.25	$256.25	$256.20
Purchase #7	$41.51	4.230%	$43.2659	$43.27	$43.25	$43.30
7 purchase totals =	$1,274.44		$1,372.4766	$1,372.47	$1,372.50	$1,372.40