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	$222.29	5.483%	$234.4782	$234.48	$234.50	$234.50
Purchase #2	$49.25	6.265%	$52.3355	$52.34	$52.35	$52.30
Purchase #3	$54.59	10.152%	$60.132	$60.13	$60.15	$60.10
Purchase #4	$70.36	9.743%	$77.2152	$77.22	$77.20	$77.20
Purchase #5	$144.32	5.419%	$152.1407	$152.14	$152.15	$152.10
Purchase #6	$70.95	12.768%	$80.0089	$80.01	$80.00	$80.00
Purchase #7	$70.88	13.696%	$80.5877	$80.59	$80.60	$80.60
7 purchase totals =	$682.64		$736.8982	$736.91	$736.95	$736.80