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	$83.50	8.302%	$90.4322	$90.43	$90.45	$90.40
Purchase #2	$91.61	8.399%	$99.3043	$99.30	$99.30	$99.30
Purchase #3	$119.38	11.735%	$133.3892	$133.39	$133.40	$133.40
Purchase #4	$179.86	3.244%	$185.6947	$185.69	$185.70	$185.70
Purchase #5	$81.27	9.212%	$88.7566	$88.76	$88.75	$88.80
Purchase #6	$118.70	11.584%	$132.4502	$132.45	$132.45	$132.50
Purchase #7	$112.33	4.416%	$117.2905	$117.29	$117.30	$117.30
7 purchase totals =	$786.65		$847.3177	$847.31	$847.35	$847.40