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	$191.69	12.830%	$216.2838	$216.28	$216.30	$216.30
Purchase #2	$118.27	11.628%	$132.0224	$132.02	$132.00	$132.00
Purchase #3	$35.55	6.401%	$37.8256	$37.83	$37.85	$37.80
Purchase #4	$90.91	12.618%	$102.381	$102.38	$102.40	$102.40
Purchase #5	$67.40	6.635%	$71.872	$71.87	$71.85	$71.90
Purchase #6	$230.35	10.156%	$253.7443	$253.74	$253.75	$253.70
Purchase #7	$240.80	10.689%	$266.5391	$266.54	$266.55	$266.50
7 purchase totals =	$974.97		$1,080.6682	$1,080.66	$1,080.70	$1,080.60