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	$140.30	9.486%	$153.6089	$153.61	$153.60	$153.60
Purchase #2	$52.58	6.361%	$55.9246	$55.92	$55.90	$55.90
Purchase #3	$85.39	5.602%	$90.1735	$90.17	$90.15	$90.20
Purchase #4	$48.66	9.778%	$53.418	$53.42	$53.40	$53.40
Purchase #5	$83.79	10.438%	$92.536	$92.54	$92.55	$92.50
Purchase #6	$39.55	7.722%	$42.6041	$42.60	$42.60	$42.60
Purchase #7	$7.66	13.378%	$8.6848	$8.68	$8.70	$8.70
7 purchase totals =	$457.93		$496.9499	$496.94	$496.90	$496.90