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	$7.63	9.613%	$8.3635	$8.36	$8.35	$8.40
Purchase #2	$190.72	5.108%	$200.462	$200.46	$200.45	$200.50
Purchase #3	$191.75	3.731%	$198.9042	$198.90	$198.90	$198.90
Purchase #4	$54.25	6.202%	$57.6146	$57.61	$57.60	$57.60
Purchase #5	$10.98	13.807%	$12.496	$12.50	$12.50	$12.50
Purchase #6	$63.37	11.707%	$70.7887	$70.79	$70.80	$70.80
Purchase #7	$192.27	4.375%	$200.6818	$200.68	$200.70	$200.70
7 purchase totals =	$710.97		$749.3108	$749.30	$749.30	$749.40