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	$229.37	5.864%	$242.8203	$242.82	$242.80	$242.80
Purchase #2	$165.28	5.450%	$174.2878	$174.29	$174.30	$174.30
Purchase #3	$183.66	7.137%	$196.7678	$196.77	$196.75	$196.80
Purchase #4	$112.25	3.872%	$116.5963	$116.60	$116.60	$116.60
Purchase #5	$171.69	13.805%	$195.3918	$195.39	$195.40	$195.40
Purchase #6	$110.39	6.851%	$117.9528	$117.95	$117.95	$118.00
Purchase #7	$82.31	9.456%	$90.0932	$90.09	$90.10	$90.10
7 purchase totals =	$1,054.95		$1,133.9100	$1,133.91	$1,133.90	$1,134.00