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	$85.25	6.679%	$90.9438	$90.94	$90.95	$90.90
Purchase #2	$167.94	6.151%	$178.27	$178.27	$178.25	$178.30
Purchase #3	$148.77	3.522%	$154.0097	$154.01	$154.00	$154.00
Purchase #4	$100.92	4.298%	$105.2575	$105.26	$105.25	$105.30
Purchase #5	$132.67	7.454%	$142.5592	$142.56	$142.55	$142.60
Purchase #6	$250.63	10.128%	$276.0138	$276.01	$276.00	$276.00
Purchase #7	$105.33	6.294%	$111.9595	$111.96	$111.95	$112.00
7 purchase totals =	$991.51		$1,059.0135	$1,059.01	$1,058.95	$1,059.10