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	$57.76	3.757%	$59.93	$59.93	$59.95	$59.90
Purchase #2	$96.25	7.525%	$103.4928	$103.49	$103.50	$103.50
Purchase #3	$227.84	5.841%	$241.1481	$241.15	$241.15	$241.10
Purchase #4	$163.75	12.435%	$184.1123	$184.11	$184.10	$184.10
Purchase #5	$119.25	7.140%	$127.7645	$127.76	$127.75	$127.80
Purchase #6	$156.32	8.322%	$169.329	$169.33	$169.35	$169.30
Purchase #7	$31.98	12.598%	$36.0088	$36.01	$36.00	$36.00
7 purchase totals =	$853.15		$921.7855	$921.78	$921.80	$921.70