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	$199.83	11.523%	$222.8564	$222.86	$222.85	$222.90
Purchase #2	$39.68	9.455%	$43.4317	$43.43	$43.45	$43.40
Purchase #3	$225.57	3.852%	$234.259	$234.26	$234.25	$234.30
Purchase #4	$168.48	3.769%	$174.83	$174.83	$174.85	$174.80
Purchase #5	$31.91	3.871%	$33.1452	$33.15	$33.15	$33.10
Purchase #6	$85.72	7.451%	$92.107	$92.11	$92.10	$92.10
Purchase #7	$161.62	8.231%	$174.9229	$174.92	$174.90	$174.90
7 purchase totals =	$912.81		$975.5522	$975.56	$975.55	$975.50