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	$95.71	8.456%	$103.8032	$103.80	$103.80	$103.80
Purchase #2	$58.60	9.872%	$64.385	$64.39	$64.40	$64.40
Purchase #3	$160.28	5.682%	$169.3871	$169.39	$169.40	$169.40
Purchase #4	$89.52	10.606%	$99.0145	$99.01	$99.00	$99.00
Purchase #5	$237.89	10.234%	$262.2357	$262.24	$262.25	$262.20
Purchase #6	$104.91	7.194%	$112.4572	$112.46	$112.45	$112.50
Purchase #7	$190.89	11.335%	$212.5274	$212.53	$212.55	$212.50
7 purchase totals =	$937.80		$1,023.8101	$1,023.82	$1,023.85	$1,023.80