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	$22.86	3.781%	$23.7243	$23.72	$23.70	$23.70
Purchase #2	$65.27	11.629%	$72.8602	$72.86	$72.85	$72.90
Purchase #3	$185.28	6.265%	$196.8878	$196.89	$196.90	$196.90
Purchase #4	$67.62	13.334%	$76.6365	$76.64	$76.65	$76.60
Purchase #5	$115.40	3.222%	$119.1182	$119.12	$119.10	$119.10
Purchase #6	$128.90	9.124%	$140.6608	$140.66	$140.65	$140.70
Purchase #7	$41.26	11.415%	$45.9698	$45.97	$45.95	$46.00
7 purchase totals =	$626.59		$675.8576	$675.86	$675.80	$675.90