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	$198.45	12.707%	$223.667	$223.67	$223.65	$223.70
Purchase #2	$117.90	12.602%	$132.7578	$132.76	$132.75	$132.80
Purchase #3	$154.93	8.346%	$167.8605	$167.86	$167.85	$167.90
Purchase #4	$56.88	4.314%	$59.3338	$59.33	$59.35	$59.30
Purchase #5	$89.55	11.331%	$99.6969	$99.70	$99.70	$99.70
Purchase #6	$193.34	4.132%	$201.3288	$201.33	$201.35	$201.30
Purchase #7	$48.38	9.136%	$52.8	$52.80	$52.80	$52.80
7 purchase totals =	$859.43		$937.4448	$937.45	$937.45	$937.50