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	$205.57	11.366%	$228.9351	$228.94	$228.95	$228.90
Purchase #2	$133.41	4.137%	$138.9292	$138.93	$138.95	$138.90
Purchase #3	$116.84	12.442%	$131.3772	$131.38	$131.40	$131.40
Purchase #4	$156.28	8.128%	$168.9824	$168.98	$169.00	$169.00
Purchase #5	$36.78	11.196%	$40.8979	$40.90	$40.90	$40.90
Purchase #6	$214.42	13.743%	$243.8877	$243.89	$243.90	$243.90
Purchase #7	$50.72	8.771%	$55.1687	$55.17	$55.15	$55.20
7 purchase totals =	$914.02		$1,008.1782	$1,008.19	$1,008.25	$1,008.20