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	$172.79	13.871%	$196.7577	$196.76	$196.75	$196.80
Purchase #2	$83.53	3.364%	$86.3399	$86.34	$86.35	$86.30
Purchase #3	$189.83	10.690%	$210.1228	$210.12	$210.10	$210.10
Purchase #4	$77.44	3.189%	$79.9096	$79.91	$79.90	$79.90
Purchase #5	$103.41	12.707%	$116.5503	$116.55	$116.55	$116.60
Purchase #6	$39.58	3.254%	$40.8679	$40.87	$40.85	$40.90
Purchase #7	$178.77	13.496%	$202.8968	$202.90	$202.90	$202.90
7 purchase totals =	$845.35		$933.4450	$933.45	$933.40	$933.50