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	$219.85	10.666%	$243.2992	$243.30	$243.30	$243.30
Purchase #2	$211.64	13.660%	$240.55	$240.55	$240.55	$240.60
Purchase #3	$240.87	5.622%	$254.4117	$254.41	$254.40	$254.40
Purchase #4	$156.33	13.155%	$176.8952	$176.90	$176.90	$176.90
Purchase #5	$64.59	6.222%	$68.6088	$68.61	$68.60	$68.60
Purchase #6	$108.36	7.502%	$116.4892	$116.49	$116.50	$116.50
Purchase #7	$72.48	8.759%	$78.8285	$78.83	$78.85	$78.80
7 purchase totals =	$1,074.12		$1,179.0826	$1,179.09	$1,179.10	$1,179.10