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	$222.35	6.195%	$236.1246	$236.12	$236.10	$236.10
Purchase #2	$63.42	13.666%	$72.087	$72.09	$72.10	$72.10
Purchase #3	$113.89	12.244%	$127.8347	$127.83	$127.85	$127.80
Purchase #4	$110.55	8.160%	$119.5709	$119.57	$119.55	$119.60
Purchase #5	$223.83	7.829%	$241.3537	$241.35	$241.35	$241.40
Purchase #6	$199.73	4.869%	$209.4549	$209.45	$209.45	$209.50
Purchase #7	$249.79	3.311%	$258.0605	$258.06	$258.05	$258.10
7 purchase totals =	$1,183.56		$1,264.4863	$1,264.47	$1,264.45	$1,264.60