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	$88.61	4.308%	$92.4273	$92.43	$92.45	$92.40
Purchase #2	$123.48	6.565%	$131.5865	$131.59	$131.60	$131.60
Purchase #3	$142.82	7.342%	$153.3058	$153.31	$153.30	$153.30
Purchase #4	$95.43	4.378%	$99.6079	$99.61	$99.60	$99.60
Purchase #5	$19.58	13.528%	$22.2288	$22.23	$22.25	$22.20
Purchase #6	$171.27	5.799%	$181.2019	$181.20	$181.20	$181.20
Purchase #7	$164.69	12.667%	$185.5513	$185.55	$185.55	$185.60
7 purchase totals =	$805.88		$865.9095	$865.92	$865.95	$865.90