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	$168.80	13.623%	$191.7956	$191.80	$191.80	$191.80
Purchase #2	$123.50	11.552%	$137.7667	$137.77	$137.75	$137.80
Purchase #3	$17.50	11.469%	$19.5071	$19.51	$19.50	$19.50
Purchase #4	$200.47	8.226%	$216.9607	$216.96	$216.95	$217.00
Purchase #5	$153.89	9.270%	$168.1556	$168.16	$168.15	$168.20
Purchase #6	$38.73	7.386%	$41.5906	$41.59	$41.60	$41.60
Purchase #7	$81.91	8.785%	$89.1058	$89.11	$89.10	$89.10
7 purchase totals =	$784.80		$864.8821	$864.90	$864.85	$865.00