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	$117.56	9.262%	$128.4484	$128.45	$128.45	$128.40
Purchase #2	$13.64	4.501%	$14.2539	$14.25	$14.25	$14.30
Purchase #3	$128.62	12.138%	$144.2319	$144.23	$144.25	$144.20
Purchase #4	$86.40	8.223%	$93.5047	$93.50	$93.50	$93.50
Purchase #5	$243.57	12.335%	$273.6144	$273.61	$273.60	$273.60
Purchase #6	$61.28	3.497%	$63.423	$63.42	$63.40	$63.40
Purchase #7	$58.69	11.774%	$65.6002	$65.60	$65.60	$65.60
7 purchase totals =	$709.76		$783.0765	$783.06	$783.05	$783.00