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	$66.87	10.481%	$73.8786	$73.88	$73.90	$73.90
Purchase #2	$97.89	3.220%	$101.0421	$101.04	$101.05	$101.00
Purchase #3	$162.82	9.328%	$178.0078	$178.01	$178.00	$178.00
Purchase #4	$114.99	7.481%	$123.5924	$123.59	$123.60	$123.60
Purchase #5	$182.47	6.570%	$194.4583	$194.46	$194.45	$194.50
Purchase #6	$7.41	6.564%	$7.8964	$7.90	$7.90	$7.90
Purchase #7	$56.73	4.491%	$59.2777	$59.28	$59.30	$59.30
7 purchase totals =	$689.18		$738.1533	$738.16	$738.20	$738.20