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	$90.33	10.537%	$99.8481	$99.85	$99.85	$99.80
Purchase #2	$40.68	6.409%	$43.2872	$43.29	$43.30	$43.30
Purchase #3	$80.83	8.753%	$87.905	$87.91	$87.90	$87.90
Purchase #4	$121.39	6.213%	$128.932	$128.93	$128.95	$128.90
Purchase #5	$37.84	8.243%	$40.9592	$40.96	$40.95	$41.00
Purchase #6	$42.43	8.271%	$45.9394	$45.94	$45.95	$45.90
Purchase #7	$229.59	10.872%	$254.551	$254.55	$254.55	$254.60
7 purchase totals =	$643.09		$701.4219	$701.43	$701.45	$701.40