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	$190.65	4.104%	$198.4743	$198.47	$198.45	$198.50
Purchase #2	$10.87	5.626%	$11.4815	$11.48	$11.50	$11.50
Purchase #3	$143.45	9.166%	$156.5986	$156.60	$156.60	$156.60
Purchase #4	$47.37	10.162%	$52.1837	$52.18	$52.20	$52.20
Purchase #5	$184.34	6.740%	$196.7645	$196.76	$196.75	$196.80
Purchase #6	$143.36	5.475%	$151.209	$151.21	$151.20	$151.20
Purchase #7	$85.81	4.663%	$89.8113	$89.81	$89.80	$89.80
7 purchase totals =	$805.85		$856.5229	$856.51	$856.50	$856.60