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	$234.31	11.155%	$260.4473	$260.45	$260.45	$260.40
Purchase #2	$212.84	11.788%	$237.9296	$237.93	$237.95	$237.90
Purchase #3	$110.27	4.179%	$114.8782	$114.88	$114.90	$114.90
Purchase #4	$195.30	13.812%	$222.2748	$222.27	$222.25	$222.30
Purchase #5	$152.93	7.814%	$164.88	$164.88	$164.90	$164.90
Purchase #6	$91.28	4.821%	$95.6806	$95.68	$95.70	$95.70
Purchase #7	$35.61	5.104%	$37.4275	$37.43	$37.45	$37.40
7 purchase totals =	$1,032.54		$1,133.5180	$1,133.52	$1,133.60	$1,133.50