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	$31.65	10.759%	$35.0552	$35.06	$35.05	$35.10
Purchase #2	$51.66	5.417%	$54.4584	$54.46	$54.45	$54.50
Purchase #3	$59.61	3.728%	$61.8323	$61.83	$61.85	$61.80
Purchase #4	$53.89	7.667%	$58.0217	$58.02	$58.00	$58.00
Purchase #5	$65.66	11.605%	$73.2798	$73.28	$73.30	$73.30
Purchase #6	$174.45	8.847%	$189.8836	$189.88	$189.90	$189.90
Purchase #7	$227.35	10.235%	$250.6193	$250.62	$250.60	$250.60
7 purchase totals =	$664.27		$723.1503	$723.15	$723.15	$723.20