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	$112.37	5.193%	$118.2054	$118.21	$118.20	$118.20
Purchase #2	$150.83	9.809%	$165.6249	$165.62	$165.60	$165.60
Purchase #3	$37.96	11.184%	$42.2054	$42.21	$42.20	$42.20
Purchase #4	$247.25	12.768%	$278.8189	$278.82	$278.80	$278.80
Purchase #5	$133.59	7.813%	$144.0274	$144.03	$144.05	$144.00
Purchase #6	$184.48	3.819%	$191.5253	$191.53	$191.55	$191.50
Purchase #7	$152.64	12.663%	$171.9688	$171.97	$171.95	$172.00
7 purchase totals =	$1,019.12		$1,112.3761	$1,112.39	$1,112.35	$1,112.30