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	$90.67	4.673%	$94.907	$94.91	$94.90	$94.90
Purchase #2	$152.29	6.227%	$161.7731	$161.77	$161.75	$161.80
Purchase #3	$219.51	6.646%	$234.0986	$234.10	$234.10	$234.10
Purchase #4	$240.71	6.844%	$257.1842	$257.18	$257.20	$257.20
Purchase #5	$99.80	5.681%	$105.4696	$105.47	$105.45	$105.50
Purchase #6	$31.82	5.285%	$33.5017	$33.50	$33.50	$33.50
Purchase #7	$137.44	10.809%	$152.2959	$152.30	$152.30	$152.30
7 purchase totals =	$972.24		$1,039.2301	$1,039.23	$1,039.20	$1,039.30