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	$203.64	9.869%	$223.7372	$223.74	$223.75	$223.70
Purchase #2	$10.79	4.423%	$11.2672	$11.27	$11.25	$11.30
Purchase #3	$190.44	13.798%	$216.7169	$216.72	$216.70	$216.70
Purchase #4	$48.37	8.732%	$52.5937	$52.59	$52.60	$52.60
Purchase #5	$108.92	8.351%	$118.0159	$118.02	$118.00	$118.00
Purchase #6	$158.47	6.278%	$168.4187	$168.42	$168.40	$168.40
Purchase #7	$92.92	8.550%	$100.8647	$100.86	$100.85	$100.90
7 purchase totals =	$813.55		$891.6143	$891.62	$891.55	$891.60