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	$113.71	13.342%	$128.8812	$128.88	$128.90	$128.90
Purchase #2	$240.67	8.492%	$261.1077	$261.11	$261.10	$261.10
Purchase #3	$88.47	7.459%	$95.069	$95.07	$95.05	$95.10
Purchase #4	$55.34	7.173%	$59.3095	$59.31	$59.30	$59.30
Purchase #5	$117.50	8.179%	$127.1103	$127.11	$127.10	$127.10
Purchase #6	$159.60	9.492%	$174.7492	$174.75	$174.75	$174.70
Purchase #7	$153.55	7.166%	$164.5534	$164.55	$164.55	$164.60
7 purchase totals =	$928.84		$1,010.7803	$1,010.78	$1,010.75	$1,010.80