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	$44.94	8.700%	$48.8498	$48.85	$48.85	$48.80
Purchase #2	$79.30	5.744%	$83.855	$83.86	$83.85	$83.90
Purchase #3	$80.33	10.156%	$88.4883	$88.49	$88.50	$88.50
Purchase #4	$6.47	10.868%	$7.1732	$7.17	$7.15	$7.20
Purchase #5	$79.87	13.522%	$90.67	$90.67	$90.65	$90.70
Purchase #6	$155.75	10.374%	$171.9075	$171.91	$171.90	$171.90
Purchase #7	$205.63	8.402%	$222.907	$222.91	$222.90	$222.90
7 purchase totals =	$652.29		$713.8508	$713.86	$713.80	$713.90