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	$194.34	13.859%	$221.2736	$221.27	$221.25	$221.30
Purchase #2	$119.75	4.356%	$124.9663	$124.97	$124.95	$125.00
Purchase #3	$14.98	6.648%	$15.9759	$15.98	$16.00	$16.00
Purchase #4	$41.79	4.619%	$43.7203	$43.72	$43.70	$43.70
Purchase #5	$95.52	3.514%	$98.8766	$98.88	$98.90	$98.90
Purchase #6	$27.96	13.820%	$31.8241	$31.82	$31.80	$31.80
Purchase #7	$150.69	11.748%	$168.3931	$168.39	$168.40	$168.40
7 purchase totals =	$645.03		$705.0299	$705.03	$705.00	$705.10