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	$238.96	3.623%	$247.6175	$247.62	$247.60	$247.60
Purchase #2	$235.72	4.274%	$245.7947	$245.79	$245.80	$245.80
Purchase #3	$152.74	9.580%	$167.3725	$167.37	$167.35	$167.40
Purchase #4	$80.90	3.317%	$83.5835	$83.58	$83.60	$83.60
Purchase #5	$155.53	11.150%	$172.8716	$172.87	$172.85	$172.90
Purchase #6	$142.36	4.838%	$149.2474	$149.25	$149.25	$149.20
Purchase #7	$63.93	13.449%	$72.5279	$72.53	$72.55	$72.50
7 purchase totals =	$1,070.14		$1,139.0151	$1,139.01	$1,139.00	$1,139.00