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	$133.40	11.424%	$148.6396	$148.64	$148.65	$148.60
Purchase #2	$89.86	11.373%	$100.0798	$100.08	$100.10	$100.10
Purchase #3	$138.47	10.405%	$152.8778	$152.88	$152.90	$152.90
Purchase #4	$192.98	7.219%	$206.9112	$206.91	$206.90	$206.90
Purchase #5	$127.64	4.206%	$133.0085	$133.01	$133.00	$133.00
Purchase #6	$145.62	7.496%	$156.5357	$156.54	$156.55	$156.50
Purchase #7	$219.84	3.146%	$226.7562	$226.76	$226.75	$226.80
7 purchase totals =	$1,047.81		$1,124.8088	$1,124.82	$1,124.85	$1,124.80