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	$198.42	11.855%	$221.9427	$221.94	$221.95	$221.90
Purchase #2	$80.59	6.226%	$85.6075	$85.61	$85.60	$85.60
Purchase #3	$125.57	11.587%	$140.1198	$140.12	$140.10	$140.10
Purchase #4	$159.71	13.661%	$181.528	$181.53	$181.55	$181.50
Purchase #5	$100.25	10.649%	$110.9256	$110.93	$110.95	$110.90
Purchase #6	$216.79	5.582%	$228.8912	$228.89	$228.90	$228.90
Purchase #7	$206.91	4.534%	$216.2913	$216.29	$216.30	$216.30
7 purchase totals =	$1,088.24		$1,185.3061	$1,185.31	$1,185.35	$1,185.20