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	$226.63	12.849%	$255.7497	$255.75	$255.75	$255.70
Purchase #2	$204.68	8.479%	$222.0348	$222.03	$222.05	$222.00
Purchase #3	$35.35	4.200%	$36.8347	$36.83	$36.85	$36.80
Purchase #4	$176.68	3.607%	$183.0528	$183.05	$183.05	$183.10
Purchase #5	$71.74	13.681%	$81.5547	$81.55	$81.55	$81.60
Purchase #6	$67.88	6.867%	$72.5413	$72.54	$72.55	$72.50
Purchase #7	$198.38	12.374%	$222.9275	$222.93	$222.95	$222.90
7 purchase totals =	$981.34		$1,074.6955	$1,074.68	$1,074.75	$1,074.60