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	$250.58	5.604%	$264.6225	$264.62	$264.60	$264.60
Purchase #2	$171.74	3.681%	$178.0617	$178.06	$178.05	$178.10
Purchase #3	$16.45	13.145%	$18.6124	$18.61	$18.60	$18.60
Purchase #4	$103.32	4.582%	$108.0541	$108.05	$108.05	$108.10
Purchase #5	$224.47	9.334%	$245.422	$245.42	$245.40	$245.40
Purchase #6	$57.70	3.102%	$59.4899	$59.49	$59.50	$59.50
Purchase #7	$156.48	9.648%	$171.5772	$171.58	$171.60	$171.60
7 purchase totals =	$980.74		$1,045.8398	$1,045.83	$1,045.80	$1,045.90