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	$119.81	9.418%	$131.0937	$131.09	$131.10	$131.10
Purchase #2	$57.97	3.535%	$60.0192	$60.02	$60.00	$60.00
Purchase #3	$188.87	13.218%	$213.8348	$213.83	$213.85	$213.80
Purchase #4	$37.98	11.279%	$42.2638	$42.26	$42.25	$42.30
Purchase #5	$203.60	8.615%	$221.1401	$221.14	$221.15	$221.10
Purchase #6	$188.38	6.490%	$200.6059	$200.61	$200.60	$200.60
Purchase #7	$140.30	10.546%	$155.096	$155.10	$155.10	$155.10
7 purchase totals =	$936.91		$1,024.0535	$1,024.05	$1,024.05	$1,024.00