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	$145.67	5.870%	$154.2208	$154.22	$154.20	$154.20
Purchase #2	$92.71	3.256%	$95.7286	$95.73	$95.75	$95.70
Purchase #3	$130.53	12.473%	$146.811	$146.81	$146.80	$146.80
Purchase #4	$208.76	11.609%	$232.9949	$232.99	$233.00	$233.00
Purchase #5	$131.43	4.443%	$137.2694	$137.27	$137.25	$137.30
Purchase #6	$189.43	3.588%	$196.2267	$196.23	$196.25	$196.20
Purchase #7	$40.59	12.256%	$45.5647	$45.56	$45.55	$45.60
7 purchase totals =	$939.12		$1,008.8161	$1,008.81	$1,008.80	$1,008.80