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	$215.73	13.843%	$245.5935	$245.59	$245.60	$245.60
Purchase #2	$171.41	5.607%	$181.021	$181.02	$181.00	$181.00
Purchase #3	$141.82	12.660%	$159.7744	$159.77	$159.75	$159.80
Purchase #4	$141.47	12.232%	$158.7746	$158.77	$158.75	$158.80
Purchase #5	$150.83	12.827%	$170.177	$170.18	$170.20	$170.20
Purchase #6	$41.87	5.119%	$44.0133	$44.01	$44.00	$44.00
Purchase #7	$78.31	4.764%	$82.0407	$82.04	$82.05	$82.00
7 purchase totals =	$941.44		$1,041.3945	$1,041.38	$1,041.35	$1,041.40