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	$10.77	8.837%	$11.7217	$11.72	$11.70	$11.70
Purchase #2	$196.38	13.225%	$222.3513	$222.35	$222.35	$222.40
Purchase #3	$76.28	6.523%	$81.2557	$81.26	$81.25	$81.30
Purchase #4	$55.49	11.693%	$61.9784	$61.98	$62.00	$62.00
Purchase #5	$150.34	8.215%	$162.6904	$162.69	$162.70	$162.70
Purchase #6	$209.61	4.221%	$218.4576	$218.46	$218.45	$218.50
Purchase #7	$233.75	11.554%	$260.7575	$260.76	$260.75	$260.80
7 purchase totals =	$932.62		$1,019.2126	$1,019.22	$1,019.20	$1,019.40