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	$196.68	3.468%	$203.5009	$203.50	$203.50	$203.50
Purchase #2	$35.59	8.713%	$38.691	$38.69	$38.70	$38.70
Purchase #3	$101.69	7.555%	$109.3727	$109.37	$109.35	$109.40
Purchase #4	$36.61	11.193%	$40.7078	$40.71	$40.70	$40.70
Purchase #5	$85.47	6.599%	$91.1102	$91.11	$91.10	$91.10
Purchase #6	$246.89	6.134%	$262.0342	$262.03	$262.05	$262.00
Purchase #7	$45.29	4.828%	$47.4766	$47.48	$47.50	$47.50
7 purchase totals =	$748.22		$792.8934	$792.89	$792.90	$792.90