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	$111.83	5.123%	$117.5591	$117.56	$117.55	$117.60
Purchase #2	$51.48	5.360%	$54.2393	$54.24	$54.25	$54.20
Purchase #3	$243.82	9.242%	$266.3538	$266.35	$266.35	$266.40
Purchase #4	$147.46	11.281%	$164.095	$164.10	$164.10	$164.10
Purchase #5	$102.84	5.849%	$108.8551	$108.86	$108.85	$108.90
Purchase #6	$228.80	11.812%	$255.8259	$255.83	$255.85	$255.80
Purchase #7	$123.49	5.751%	$130.5919	$130.59	$130.60	$130.60
7 purchase totals =	$1,009.72		$1,097.5201	$1,097.53	$1,097.55	$1,097.60