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	$189.36	4.827%	$198.5004	$198.50	$198.50	$198.50
Purchase #2	$59.44	8.321%	$64.386	$64.39	$64.40	$64.40
Purchase #3	$91.41	4.631%	$95.6432	$95.64	$95.65	$95.60
Purchase #4	$40.97	3.821%	$42.5355	$42.54	$42.55	$42.50
Purchase #5	$154.82	9.603%	$169.6874	$169.69	$169.70	$169.70
Purchase #6	$182.60	4.145%	$190.1688	$190.17	$190.15	$190.20
Purchase #7	$130.65	9.565%	$143.1467	$143.15	$143.15	$143.10
7 purchase totals =	$849.25		$904.0680	$904.08	$904.10	$904.00