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	$228.68	8.670%	$248.5066	$248.51	$248.50	$248.50
Purchase #2	$92.37	6.579%	$98.447	$98.45	$98.45	$98.40
Purchase #3	$172.54	10.522%	$190.6947	$190.69	$190.70	$190.70
Purchase #4	$168.71	7.642%	$181.6028	$181.60	$181.60	$181.60
Purchase #5	$55.42	6.325%	$58.9253	$58.93	$58.95	$58.90
Purchase #6	$182.31	3.443%	$188.5869	$188.59	$188.60	$188.60
Purchase #7	$150.77	9.128%	$164.5323	$164.53	$164.55	$164.50
7 purchase totals =	$1,050.80		$1,131.2956	$1,131.30	$1,131.35	$1,131.20