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	$59.38	6.127%	$63.0182	$63.02	$63.00	$63.00
Purchase #2	$37.50	12.309%	$42.1159	$42.12	$42.10	$42.10
Purchase #3	$34.80	12.306%	$39.0825	$39.08	$39.10	$39.10
Purchase #4	$119.87	6.563%	$127.7371	$127.74	$127.75	$127.70
Purchase #5	$61.26	9.640%	$67.1655	$67.17	$67.15	$67.20
Purchase #6	$52.76	9.789%	$57.9247	$57.92	$57.90	$57.90
Purchase #7	$164.34	4.104%	$171.0845	$171.08	$171.10	$171.10
7 purchase totals =	$529.91		$568.1284	$568.13	$568.10	$568.10