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	$151.60	9.204%	$165.5533	$165.55	$165.55	$165.60
Purchase #2	$35.82	5.565%	$37.8134	$37.81	$37.80	$37.80
Purchase #3	$43.84	7.346%	$47.0605	$47.06	$47.05	$47.10
Purchase #4	$122.93	7.292%	$131.8941	$131.89	$131.90	$131.90
Purchase #5	$65.64	10.821%	$72.7429	$72.74	$72.75	$72.70
Purchase #6	$115.40	11.123%	$128.2359	$128.24	$128.25	$128.20
Purchase #7	$50.34	4.404%	$52.557	$52.56	$52.55	$52.60
7 purchase totals =	$585.57		$635.8571	$635.85	$635.85	$635.90