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	$173.72	4.534%	$181.5965	$181.60	$181.60	$181.60
Purchase #2	$157.58	4.202%	$164.2015	$164.20	$164.20	$164.20
Purchase #3	$228.28	6.655%	$243.472	$243.47	$243.45	$243.50
Purchase #4	$206.25	11.301%	$229.5583	$229.56	$229.55	$229.60
Purchase #5	$168.97	6.761%	$180.3941	$180.39	$180.40	$180.40
Purchase #6	$24.93	10.560%	$27.5626	$27.56	$27.55	$27.60
Purchase #7	$75.89	4.155%	$79.0432	$79.04	$79.05	$79.00
7 purchase totals =	$1,035.62		$1,105.8282	$1,105.82	$1,105.80	$1,105.90