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	$247.65	12.705%	$279.1139	$279.11	$279.10	$279.10
Purchase #2	$213.35	4.686%	$223.3476	$223.35	$223.35	$223.30
Purchase #3	$91.61	7.364%	$98.3562	$98.36	$98.35	$98.40
Purchase #4	$180.48	6.323%	$191.8918	$191.89	$191.90	$191.90
Purchase #5	$76.84	7.576%	$82.6614	$82.66	$82.65	$82.70
Purchase #6	$42.34	7.390%	$45.4689	$45.47	$45.45	$45.50
Purchase #7	$178.49	3.552%	$184.83	$184.83	$184.85	$184.80
7 purchase totals =	$1,030.76		$1,105.6698	$1,105.67	$1,105.65	$1,105.70