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	$167.47	11.678%	$187.0271	$187.03	$187.05	$187.00
Purchase #2	$222.70	8.873%	$242.4602	$242.46	$242.45	$242.50
Purchase #3	$44.79	10.851%	$49.6502	$49.65	$49.65	$49.70
Purchase #4	$152.95	13.499%	$173.5967	$173.60	$173.60	$173.60
Purchase #5	$71.39	9.271%	$78.0086	$78.01	$78.00	$78.00
Purchase #6	$56.78	8.673%	$61.7045	$61.70	$61.70	$61.70
Purchase #7	$212.27	3.275%	$219.2218	$219.22	$219.20	$219.20
7 purchase totals =	$928.35		$1,011.6691	$1,011.67	$1,011.65	$1,011.70