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	$144.80	9.300%	$158.2664	$158.27	$158.25	$158.30
Purchase #2	$237.34	4.855%	$248.8629	$248.86	$248.85	$248.90
Purchase #3	$194.49	3.273%	$200.8557	$200.86	$200.85	$200.90
Purchase #4	$181.48	10.723%	$200.9401	$200.94	$200.95	$200.90
Purchase #5	$39.33	10.384%	$43.414	$43.41	$43.40	$43.40
Purchase #6	$141.62	13.325%	$160.4909	$160.49	$160.50	$160.50
Purchase #7	$206.79	12.321%	$232.2686	$232.27	$232.25	$232.30
7 purchase totals =	$1,145.85		$1,245.0986	$1,245.10	$1,245.05	$1,245.20