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	$249.32	4.605%	$260.8012	$260.80	$260.80	$260.80
Purchase #2	$240.74	6.136%	$255.5118	$255.51	$255.50	$255.50
Purchase #3	$209.63	5.521%	$221.2037	$221.20	$221.20	$221.20
Purchase #4	$39.54	13.355%	$44.8206	$44.82	$44.80	$44.80
Purchase #5	$193.82	11.185%	$215.4988	$215.50	$215.50	$215.50
Purchase #6	$105.82	5.254%	$111.3798	$111.38	$111.40	$111.40
Purchase #7	$224.64	11.670%	$250.8555	$250.86	$250.85	$250.90
7 purchase totals =	$1,263.51		$1,360.0714	$1,360.07	$1,360.05	$1,360.10