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	$56.61	5.607%	$59.7841	$59.78	$59.80	$59.80
Purchase #2	$74.78	6.297%	$79.4889	$79.49	$79.50	$79.50
Purchase #3	$31.39	10.773%	$34.7716	$34.77	$34.75	$34.80
Purchase #4	$50.66	10.376%	$55.9165	$55.92	$55.90	$55.90
Purchase #5	$192.43	4.438%	$200.97	$200.97	$200.95	$201.00
Purchase #6	$203.43	4.428%	$212.4379	$212.44	$212.45	$212.40
Purchase #7	$131.61	12.818%	$148.4798	$148.48	$148.50	$148.50
7 purchase totals =	$740.91		$791.8488	$791.85	$791.85	$791.90