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	$149.48	12.284%	$167.8421	$167.84	$167.85	$167.80
Purchase #2	$187.77	13.284%	$212.7134	$212.71	$212.70	$212.70
Purchase #3	$73.77	9.648%	$80.8873	$80.89	$80.90	$80.90
Purchase #4	$28.40	7.201%	$30.4451	$30.45	$30.45	$30.40
Purchase #5	$112.58	12.863%	$127.0612	$127.06	$127.05	$127.10
Purchase #6	$248.45	4.564%	$259.7893	$259.79	$259.80	$259.80
Purchase #7	$242.43	13.771%	$275.815	$275.82	$275.80	$275.80
7 purchase totals =	$1,042.88		$1,154.5534	$1,154.56	$1,154.55	$1,154.50