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	$142.86	4.456%	$149.2258	$149.23	$149.25	$149.20
Purchase #2	$114.96	11.831%	$128.5609	$128.56	$128.55	$128.60
Purchase #3	$96.51	7.162%	$103.422	$103.42	$103.40	$103.40
Purchase #4	$29.60	6.310%	$31.4678	$31.47	$31.45	$31.50
Purchase #5	$48.66	7.743%	$52.4277	$52.43	$52.45	$52.40
Purchase #6	$73.34	9.663%	$80.4268	$80.43	$80.45	$80.40
Purchase #7	$124.48	6.523%	$132.5998	$132.60	$132.60	$132.60
7 purchase totals =	$630.41		$678.1308	$678.14	$678.15	$678.10