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	$157.67	10.298%	$173.9069	$173.91	$173.90	$173.90
Purchase #2	$194.54	11.172%	$216.274	$216.27	$216.25	$216.30
Purchase #3	$33.37	5.415%	$35.177	$35.18	$35.20	$35.20
Purchase #4	$239.56	9.346%	$261.9493	$261.95	$261.95	$261.90
Purchase #5	$56.61	8.521%	$61.4337	$61.43	$61.45	$61.40
Purchase #6	$124.92	5.356%	$131.6107	$131.61	$131.60	$131.60
Purchase #7	$181.89	10.275%	$200.5792	$200.58	$200.60	$200.60
7 purchase totals =	$988.56		$1,080.9308	$1,080.93	$1,080.95	$1,080.90