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	$6.94	11.684%	$7.7509	$7.75	$7.75	$7.80
Purchase #2	$154.33	9.530%	$169.0376	$169.04	$169.05	$169.00
Purchase #3	$64.49	11.727%	$72.0527	$72.05	$72.05	$72.10
Purchase #4	$239.43	7.500%	$257.3873	$257.39	$257.40	$257.40
Purchase #5	$85.78	11.443%	$95.5958	$95.60	$95.60	$95.60
Purchase #6	$110.38	6.740%	$117.8196	$117.82	$117.80	$117.80
Purchase #7	$165.55	5.466%	$174.599	$174.60	$174.60	$174.60
7 purchase totals =	$826.90		$894.2429	$894.25	$894.25	$894.30