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	$119.77	3.453%	$123.9057	$123.91	$123.90	$123.90
Purchase #2	$162.37	3.118%	$167.4327	$167.43	$167.45	$167.40
Purchase #3	$211.95	5.313%	$223.2109	$223.21	$223.20	$223.20
Purchase #4	$203.90	10.125%	$224.5449	$224.54	$224.55	$224.50
Purchase #5	$109.72	4.782%	$114.9668	$114.97	$114.95	$115.00
Purchase #6	$84.83	11.227%	$94.3539	$94.35	$94.35	$94.40
Purchase #7	$75.64	3.292%	$78.1301	$78.13	$78.15	$78.10
7 purchase totals =	$968.18		$1,026.5450	$1,026.54	$1,026.55	$1,026.50