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	$29.90	12.114%	$33.5221	$33.52	$33.50	$33.50
Purchase #2	$110.27	6.656%	$117.6096	$117.61	$117.60	$117.60
Purchase #3	$57.78	3.212%	$59.6359	$59.64	$59.65	$59.60
Purchase #4	$81.96	8.439%	$88.8766	$88.88	$88.90	$88.90
Purchase #5	$170.69	8.344%	$184.9324	$184.93	$184.95	$184.90
Purchase #6	$151.30	11.461%	$168.6405	$168.64	$168.65	$168.60
Purchase #7	$124.32	6.122%	$131.9309	$131.93	$131.95	$131.90
7 purchase totals =	$726.22		$785.1480	$785.15	$785.20	$785.00