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	$101.35	4.811%	$106.2259	$106.23	$106.25	$106.20
Purchase #2	$27.97	3.357%	$28.909	$28.91	$28.90	$28.90
Purchase #3	$38.88	11.742%	$43.4453	$43.45	$43.45	$43.40
Purchase #4	$68.98	13.690%	$78.4234	$78.42	$78.40	$78.40
Purchase #5	$182.78	5.327%	$192.5167	$192.52	$192.50	$192.50
Purchase #6	$104.91	6.245%	$111.4616	$111.46	$111.45	$111.50
Purchase #7	$84.71	5.457%	$89.3326	$89.33	$89.35	$89.30
7 purchase totals =	$609.58		$650.3145	$650.32	$650.30	$650.20