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	$73.76	10.825%	$81.7445	$81.74	$81.75	$81.70
Purchase #2	$175.93	7.571%	$189.2497	$189.25	$189.25	$189.20
Purchase #3	$114.85	11.117%	$127.6179	$127.62	$127.60	$127.60
Purchase #4	$152.83	3.740%	$158.5458	$158.55	$158.55	$158.50
Purchase #5	$28.80	11.829%	$32.2068	$32.21	$32.20	$32.20
Purchase #6	$241.53	6.181%	$256.459	$256.46	$256.45	$256.50
Purchase #7	$212.35	4.295%	$221.4704	$221.47	$221.45	$221.50
7 purchase totals =	$1,000.05		$1,067.2941	$1,067.30	$1,067.25	$1,067.20