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	$140.43	3.495%	$145.338	$145.34	$145.35	$145.30
Purchase #2	$125.62	13.506%	$142.5862	$142.59	$142.60	$142.60
Purchase #3	$32.47	13.309%	$36.7914	$36.79	$36.80	$36.80
Purchase #4	$235.39	13.791%	$267.8526	$267.85	$267.85	$267.90
Purchase #5	$89.35	11.473%	$99.6011	$99.60	$99.60	$99.60
Purchase #6	$35.32	11.458%	$39.367	$39.37	$39.35	$39.40
Purchase #7	$184.48	3.676%	$191.2615	$191.26	$191.25	$191.30
7 purchase totals =	$843.06		$922.7978	$922.80	$922.80	$922.90