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	$195.57	13.603%	$222.1734	$222.17	$222.15	$222.20
Purchase #2	$103.58	3.541%	$107.2478	$107.25	$107.25	$107.20
Purchase #3	$100.77	13.829%	$114.7055	$114.71	$114.70	$114.70
Purchase #4	$142.46	4.282%	$148.5601	$148.56	$148.55	$148.60
Purchase #5	$5.33	5.648%	$5.631	$5.63	$5.65	$5.60
Purchase #6	$64.92	11.812%	$72.5884	$72.59	$72.60	$72.60
Purchase #7	$218.48	10.473%	$241.3614	$241.36	$241.35	$241.40
7 purchase totals =	$831.11		$912.2676	$912.27	$912.25	$912.30