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	$52.50	4.305%	$54.7601	$54.76	$54.75	$54.80
Purchase #2	$9.45	6.442%	$10.0588	$10.06	$10.05	$10.10
Purchase #3	$99.57	6.391%	$105.9335	$105.93	$105.95	$105.90
Purchase #4	$215.96	7.551%	$232.2671	$232.27	$232.25	$232.30
Purchase #5	$152.94	11.689%	$170.8172	$170.82	$170.80	$170.80
Purchase #6	$83.83	7.618%	$90.2162	$90.22	$90.20	$90.20
Purchase #7	$141.92	5.734%	$150.0577	$150.06	$150.05	$150.10
7 purchase totals =	$756.17		$814.1106	$814.12	$814.05	$814.20