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	$77.33	3.714%	$80.202	$80.20	$80.20	$80.20
Purchase #2	$76.85	7.446%	$82.5723	$82.57	$82.55	$82.60
Purchase #3	$180.73	6.215%	$191.9624	$191.96	$191.95	$192.00
Purchase #4	$246.90	13.414%	$280.0192	$280.02	$280.00	$280.00
Purchase #5	$103.51	7.765%	$111.5476	$111.55	$111.55	$111.50
Purchase #6	$57.44	8.505%	$62.3253	$62.33	$62.35	$62.30
Purchase #7	$63.49	3.180%	$65.509	$65.51	$65.50	$65.50
7 purchase totals =	$806.25		$874.1378	$874.14	$874.10	$874.10