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	$137.47	7.646%	$147.981	$147.98	$148.00	$148.00
Purchase #2	$59.39	11.226%	$66.0571	$66.06	$66.05	$66.10
Purchase #3	$31.59	3.250%	$32.6167	$32.62	$32.60	$32.60
Purchase #4	$193.60	5.615%	$204.4706	$204.47	$204.45	$204.50
Purchase #5	$247.36	13.435%	$280.5928	$280.59	$280.60	$280.60
Purchase #6	$190.28	7.752%	$205.0305	$205.03	$205.05	$205.00
Purchase #7	$101.47	8.520%	$110.1152	$110.12	$110.10	$110.10
7 purchase totals =	$961.16		$1,046.8639	$1,046.87	$1,046.85	$1,046.90