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	$42.33	9.410%	$46.3133	$46.31	$46.30	$46.30
Purchase #2	$185.51	6.118%	$196.8595	$196.86	$196.85	$196.90
Purchase #3	$85.78	9.145%	$93.6246	$93.62	$93.60	$93.60
Purchase #4	$244.93	11.529%	$273.168	$273.17	$273.15	$273.20
Purchase #5	$98.47	4.522%	$102.9228	$102.92	$102.90	$102.90
Purchase #6	$178.55	10.301%	$196.9424	$196.94	$196.95	$196.90
Purchase #7	$207.94	11.660%	$232.1858	$232.19	$232.20	$232.20
7 purchase totals =	$1,043.51		$1,142.0164	$1,142.01	$1,141.95	$1,142.00