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	$92.75	13.840%	$105.5866	$105.59	$105.60	$105.60
Purchase #2	$89.68	7.404%	$96.3199	$96.32	$96.30	$96.30
Purchase #3	$81.44	7.660%	$87.6783	$87.68	$87.70	$87.70
Purchase #4	$183.37	9.407%	$200.6196	$200.62	$200.60	$200.60
Purchase #5	$32.44	9.614%	$35.5588	$35.56	$35.55	$35.60
Purchase #6	$119.67	12.433%	$134.5486	$134.55	$134.55	$134.50
Purchase #7	$191.40	4.551%	$200.1106	$200.11	$200.10	$200.10
7 purchase totals =	$790.75		$860.4224	$860.43	$860.40	$860.40