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	$130.90	8.142%	$141.5579	$141.56	$141.55	$141.60
Purchase #2	$171.72	5.307%	$180.8332	$180.83	$180.85	$180.80
Purchase #3	$32.53	9.786%	$35.7134	$35.71	$35.70	$35.70
Purchase #4	$168.57	12.867%	$190.2599	$190.26	$190.25	$190.30
Purchase #5	$130.89	13.256%	$148.2408	$148.24	$148.25	$148.20
Purchase #6	$203.38	7.230%	$218.0844	$218.08	$218.10	$218.10
Purchase #7	$170.55	4.419%	$178.0866	$178.09	$178.10	$178.10
7 purchase totals =	$1,008.54		$1,092.7762	$1,092.77	$1,092.80	$1,092.80