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	$9.45	8.147%	$10.2199	$10.22	$10.20	$10.20
Purchase #2	$72.26	8.676%	$78.5293	$78.53	$78.55	$78.50
Purchase #3	$120.56	8.564%	$130.8848	$130.88	$130.90	$130.90
Purchase #4	$84.59	3.200%	$87.2969	$87.30	$87.30	$87.30
Purchase #5	$154.55	11.228%	$171.9029	$171.90	$171.90	$171.90
Purchase #6	$118.48	7.235%	$127.052	$127.05	$127.05	$127.10
Purchase #7	$120.92	6.111%	$128.3094	$128.31	$128.30	$128.30
7 purchase totals =	$680.81		$734.1952	$734.19	$734.20	$734.20