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	$176.43	12.434%	$198.3673	$198.37	$198.35	$198.40
Purchase #2	$43.48	5.505%	$45.8736	$45.87	$45.85	$45.90
Purchase #3	$211.85	3.364%	$218.9766	$218.98	$219.00	$219.00
Purchase #4	$54.99	13.815%	$62.5869	$62.59	$62.60	$62.60
Purchase #5	$134.52	10.150%	$148.1738	$148.17	$148.15	$148.20
Purchase #6	$42.32	6.163%	$44.9282	$44.93	$44.95	$44.90
Purchase #7	$178.53	12.424%	$200.7106	$200.71	$200.70	$200.70
7 purchase totals =	$842.12		$919.6170	$919.62	$919.60	$919.70