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	$191.79	9.259%	$209.5478	$209.55	$209.55	$209.50
Purchase #2	$127.98	13.479%	$145.2304	$145.23	$145.25	$145.20
Purchase #3	$130.37	5.402%	$137.4126	$137.41	$137.40	$137.40
Purchase #4	$18.83	11.368%	$20.9706	$20.97	$20.95	$21.00
Purchase #5	$50.90	5.305%	$53.6002	$53.60	$53.60	$53.60
Purchase #6	$56.41	13.260%	$63.89	$63.89	$63.90	$63.90
Purchase #7	$86.41	10.826%	$95.7647	$95.76	$95.75	$95.80
7 purchase totals =	$662.69		$726.4163	$726.41	$726.40	$726.40