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	$62.63	6.572%	$66.746	$66.75	$66.75	$66.70
Purchase #2	$144.46	4.834%	$151.4432	$151.44	$151.45	$151.40
Purchase #3	$143.30	5.301%	$150.8963	$150.90	$150.90	$150.90
Purchase #4	$79.84	13.646%	$90.735	$90.74	$90.75	$90.70
Purchase #5	$240.51	7.461%	$258.4545	$258.45	$258.45	$258.50
Purchase #6	$56.96	13.226%	$64.4935	$64.49	$64.50	$64.50
Purchase #7	$126.41	5.242%	$133.0364	$133.04	$133.05	$133.00
7 purchase totals =	$854.11		$915.8049	$915.81	$915.85	$915.70