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	$97.98	13.116%	$110.8311	$110.83	$110.85	$110.80
Purchase #2	$76.53	9.611%	$83.8853	$83.89	$83.90	$83.90
Purchase #3	$244.34	9.369%	$267.2322	$267.23	$267.25	$267.20
Purchase #4	$196.60	3.168%	$202.8283	$202.83	$202.85	$202.80
Purchase #5	$158.41	12.805%	$178.6944	$178.69	$178.70	$178.70
Purchase #6	$48.72	3.656%	$50.5012	$50.50	$50.50	$50.50
Purchase #7	$128.82	12.845%	$145.3669	$145.37	$145.35	$145.40
7 purchase totals =	$951.40		$1,039.3394	$1,039.34	$1,039.40	$1,039.30