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	$147.79	11.301%	$164.4917	$164.49	$164.50	$164.50
Purchase #2	$85.31	4.177%	$88.8734	$88.87	$88.85	$88.90
Purchase #3	$190.56	4.460%	$199.059	$199.06	$199.05	$199.10
Purchase #4	$217.57	13.652%	$247.2727	$247.27	$247.25	$247.30
Purchase #5	$207.34	6.472%	$220.759	$220.76	$220.75	$220.80
Purchase #6	$76.56	7.631%	$82.4023	$82.40	$82.40	$82.40
Purchase #7	$64.83	12.110%	$72.6809	$72.68	$72.70	$72.70
7 purchase totals =	$989.96		$1,075.5390	$1,075.53	$1,075.50	$1,075.70