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	$94.95	4.150%	$98.8904	$98.89	$98.90	$98.90
Purchase #2	$72.43	13.535%	$82.2334	$82.23	$82.25	$82.20
Purchase #3	$10.68	11.419%	$11.8995	$11.90	$11.90	$11.90
Purchase #4	$142.76	9.420%	$156.208	$156.21	$156.20	$156.20
Purchase #5	$89.60	11.271%	$99.6988	$99.70	$99.70	$99.70
Purchase #6	$178.56	10.534%	$197.3695	$197.37	$197.35	$197.40
Purchase #7	$156.62	8.388%	$169.7573	$169.76	$169.75	$169.80
7 purchase totals =	$745.60		$816.0569	$816.06	$816.05	$816.10