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	$166.49	3.256%	$171.9109	$171.91	$171.90	$171.90
Purchase #2	$119.46	3.546%	$123.6961	$123.70	$123.70	$123.70
Purchase #3	$241.46	10.507%	$266.8302	$266.83	$266.85	$266.80
Purchase #4	$233.81	4.748%	$244.9113	$244.91	$244.90	$244.90
Purchase #5	$97.77	3.150%	$100.8498	$100.85	$100.85	$100.80
Purchase #6	$180.77	13.515%	$205.2011	$205.20	$205.20	$205.20
Purchase #7	$241.89	10.356%	$266.9401	$266.94	$266.95	$266.90
7 purchase totals =	$1,281.65		$1,380.3395	$1,380.34	$1,380.35	$1,380.20