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	$234.92	11.254%	$261.3579	$261.36	$261.35	$261.40
Purchase #2	$83.41	7.201%	$89.4164	$89.42	$89.40	$89.40
Purchase #3	$124.56	6.658%	$132.8532	$132.85	$132.85	$132.90
Purchase #4	$108.48	4.229%	$113.0676	$113.07	$113.05	$113.10
Purchase #5	$197.53	11.123%	$219.5013	$219.50	$219.50	$219.50
Purchase #6	$196.30	5.248%	$206.6018	$206.60	$206.60	$206.60
Purchase #7	$237.86	13.873%	$270.8583	$270.86	$270.85	$270.90
7 purchase totals =	$1,183.06		$1,293.6565	$1,293.66	$1,293.60	$1,293.80