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	$128.36	3.415%	$132.7435	$132.74	$132.75	$132.70
Purchase #2	$99.27	6.392%	$105.6153	$105.62	$105.60	$105.60
Purchase #3	$35.46	8.295%	$38.4014	$38.40	$38.40	$38.40
Purchase #4	$142.49	8.825%	$155.0647	$155.06	$155.05	$155.10
Purchase #5	$47.66	13.567%	$54.126	$54.13	$54.15	$54.10
Purchase #6	$42.72	7.579%	$45.9577	$45.96	$45.95	$46.00
Purchase #7	$59.75	6.223%	$63.4682	$63.47	$63.45	$63.50
7 purchase totals =	$555.71		$595.3768	$595.38	$595.35	$595.40