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	$35.47	4.586%	$37.0967	$37.10	$37.10	$37.10
Purchase #2	$211.39	4.161%	$220.1859	$220.19	$220.20	$220.20
Purchase #3	$14.33	7.127%	$15.3513	$15.35	$15.35	$15.40
Purchase #4	$85.69	4.452%	$89.5049	$89.50	$89.50	$89.50
Purchase #5	$168.30	8.209%	$182.1157	$182.12	$182.10	$182.10
Purchase #6	$126.71	11.586%	$141.3906	$141.39	$141.40	$141.40
Purchase #7	$99.25	12.722%	$111.8766	$111.88	$111.90	$111.90
7 purchase totals =	$741.14		$797.5217	$797.53	$797.55	$797.60