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	$228.92	3.689%	$237.3649	$237.36	$237.35	$237.40
Purchase #2	$128.79	5.752%	$136.198	$136.20	$136.20	$136.20
Purchase #3	$161.56	10.363%	$178.3025	$178.30	$178.30	$178.30
Purchase #4	$177.72	10.675%	$196.6916	$196.69	$196.70	$196.70
Purchase #5	$83.25	10.650%	$92.1161	$92.12	$92.10	$92.10
Purchase #6	$207.78	10.254%	$229.0858	$229.09	$229.10	$229.10
Purchase #7	$153.37	12.692%	$172.8357	$172.84	$172.85	$172.80
7 purchase totals =	$1,141.39		$1,242.5946	$1,242.60	$1,242.60	$1,242.60