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	$92.43	5.387%	$97.4092	$97.41	$97.40	$97.40
Purchase #2	$33.54	5.775%	$35.4769	$35.48	$35.50	$35.50
Purchase #3	$173.64	3.420%	$179.5785	$179.58	$179.60	$179.60
Purchase #4	$63.70	13.801%	$72.4912	$72.49	$72.50	$72.50
Purchase #5	$52.53	7.862%	$56.6599	$56.66	$56.65	$56.70
Purchase #6	$215.79	8.260%	$233.6143	$233.61	$233.60	$233.60
Purchase #7	$19.88	3.771%	$20.6297	$20.63	$20.65	$20.60
7 purchase totals =	$651.51		$695.8597	$695.86	$695.90	$695.90