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	$35.32	4.670%	$36.9694	$36.97	$36.95	$37.00
Purchase #2	$211.74	5.161%	$222.6679	$222.67	$222.65	$222.70
Purchase #3	$100.34	11.498%	$111.8771	$111.88	$111.90	$111.90
Purchase #4	$168.41	10.197%	$185.5828	$185.58	$185.60	$185.60
Purchase #5	$103.74	5.798%	$109.7548	$109.75	$109.75	$109.80
Purchase #6	$27.95	5.656%	$29.5309	$29.53	$29.55	$29.50
Purchase #7	$130.27	7.204%	$139.6547	$139.65	$139.65	$139.70
7 purchase totals =	$777.77		$836.0376	$836.03	$836.05	$836.20