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	$36.81	10.589%	$40.7078	$40.71	$40.70	$40.70
Purchase #2	$86.71	10.730%	$96.014	$96.01	$96.00	$96.00
Purchase #3	$6.76	12.277%	$7.5899	$7.59	$7.60	$7.60
Purchase #4	$72.71	12.860%	$82.0605	$82.06	$82.05	$82.10
Purchase #5	$166.34	13.628%	$189.0088	$189.01	$189.00	$189.00
Purchase #6	$124.38	5.416%	$131.1164	$131.12	$131.10	$131.10
Purchase #7	$140.51	7.616%	$151.2112	$151.21	$151.20	$151.20
7 purchase totals =	$634.22		$697.7086	$697.71	$697.65	$697.70