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	$74.34	10.244%	$81.9554	$81.96	$81.95	$82.00
Purchase #2	$156.85	13.512%	$178.0436	$178.04	$178.05	$178.00
Purchase #3	$211.29	10.329%	$233.1141	$233.11	$233.10	$233.10
Purchase #4	$250.80	11.736%	$280.2339	$280.23	$280.25	$280.20
Purchase #5	$152.28	11.351%	$169.5653	$169.57	$169.55	$169.60
Purchase #6	$28.72	8.245%	$31.088	$31.09	$31.10	$31.10
Purchase #7	$99.62	5.216%	$104.8162	$104.82	$104.80	$104.80
7 purchase totals =	$973.90		$1,078.8165	$1,078.82	$1,078.80	$1,078.80