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	$129.61	8.768%	$140.9742	$140.97	$140.95	$141.00
Purchase #2	$196.82	6.566%	$209.7432	$209.74	$209.75	$209.70
Purchase #3	$222.38	4.538%	$232.4716	$232.47	$232.45	$232.50
Purchase #4	$91.80	9.297%	$100.3346	$100.33	$100.35	$100.30
Purchase #5	$57.77	11.584%	$64.4621	$64.46	$64.45	$64.50
Purchase #6	$97.80	12.303%	$109.8323	$109.83	$109.85	$109.80
Purchase #7	$176.90	3.792%	$183.608	$183.61	$183.60	$183.60
7 purchase totals =	$973.08		$1,041.4260	$1,041.41	$1,041.40	$1,041.40