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	$97.64	13.161%	$110.4904	$110.49	$110.50	$110.50
Purchase #2	$76.97	6.720%	$82.1424	$82.14	$82.15	$82.10
Purchase #3	$76.98	7.298%	$82.598	$82.60	$82.60	$82.60
Purchase #4	$202.51	13.528%	$229.9056	$229.91	$229.90	$229.90
Purchase #5	$91.86	8.445%	$99.6176	$99.62	$99.60	$99.60
Purchase #6	$101.57	12.818%	$114.5892	$114.59	$114.60	$114.60
Purchase #7	$46.71	10.855%	$51.7804	$51.78	$51.80	$51.80
7 purchase totals =	$694.24		$771.1236	$771.13	$771.15	$771.10