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	$95.59	3.780%	$99.2033	$99.20	$99.20	$99.20
Purchase #2	$82.44	6.474%	$87.7772	$87.78	$87.80	$87.80
Purchase #3	$46.47	12.743%	$52.3917	$52.39	$52.40	$52.40
Purchase #4	$51.65	4.416%	$53.9309	$53.93	$53.95	$53.90
Purchase #5	$55.34	6.730%	$59.0644	$59.06	$59.05	$59.10
Purchase #6	$108.44	11.325%	$120.7208	$120.72	$120.70	$120.70
Purchase #7	$167.64	7.323%	$179.9163	$179.92	$179.90	$179.90
7 purchase totals =	$607.57		$653.0046	$653.00	$653.00	$653.00