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	$71.69	3.228%	$74.0042	$74.00	$74.00	$74.00
Purchase #2	$165.36	12.435%	$185.9225	$185.92	$185.90	$185.90
Purchase #3	$155.95	5.356%	$164.3027	$164.30	$164.30	$164.30
Purchase #4	$49.78	9.678%	$54.5977	$54.60	$54.60	$54.60
Purchase #5	$200.88	6.370%	$213.6761	$213.68	$213.70	$213.70
Purchase #6	$54.95	12.544%	$61.8429	$61.84	$61.85	$61.80
Purchase #7	$165.52	11.271%	$184.1758	$184.18	$184.20	$184.20
7 purchase totals =	$864.13		$938.5219	$938.52	$938.55	$938.50