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	$118.42	13.303%	$134.1734	$134.17	$134.15	$134.20
Purchase #2	$98.93	12.681%	$111.4753	$111.48	$111.50	$111.50
Purchase #3	$30.68	5.346%	$32.3202	$32.32	$32.30	$32.30
Purchase #4	$244.65	8.483%	$265.4037	$265.40	$265.40	$265.40
Purchase #5	$87.25	8.158%	$94.3679	$94.37	$94.35	$94.40
Purchase #6	$84.56	12.700%	$95.2991	$95.30	$95.30	$95.30
Purchase #7	$31.44	4.617%	$32.8916	$32.89	$32.90	$32.90
7 purchase totals =	$695.93		$765.9312	$765.93	$765.90	$766.00