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	$114.93	4.173%	$119.726	$119.73	$119.75	$119.70
Purchase #2	$14.54	4.865%	$15.2474	$15.25	$15.25	$15.20
Purchase #3	$94.38	5.145%	$99.2359	$99.24	$99.25	$99.20
Purchase #4	$190.95	6.231%	$202.8481	$202.85	$202.85	$202.80
Purchase #5	$140.78	3.171%	$145.2441	$145.24	$145.25	$145.20
Purchase #6	$103.69	12.312%	$116.4563	$116.46	$116.45	$116.50
Purchase #7	$63.93	6.178%	$67.8796	$67.88	$67.90	$67.90
7 purchase totals =	$723.20		$766.6374	$766.65	$766.70	$766.50