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	$24.51	10.400%	$27.059	$27.06	$27.05	$27.10
Purchase #2	$204.89	6.197%	$217.587	$217.59	$217.60	$217.60
Purchase #3	$136.89	10.132%	$150.7597	$150.76	$150.75	$150.80
Purchase #4	$156.82	9.546%	$171.79	$171.79	$171.80	$171.80
Purchase #5	$167.62	10.703%	$185.5604	$185.56	$185.55	$185.60
Purchase #6	$214.96	4.164%	$223.9109	$223.91	$223.90	$223.90
Purchase #7	$124.58	12.636%	$140.3219	$140.32	$140.30	$140.30
7 purchase totals =	$1,030.27		$1,116.9889	$1,116.99	$1,116.95	$1,117.10