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	$185.27	4.703%	$193.9832	$193.98	$194.00	$194.00
Purchase #2	$86.87	6.441%	$92.4653	$92.47	$92.45	$92.50
Purchase #3	$155.61	9.222%	$169.9604	$169.96	$169.95	$170.00
Purchase #4	$18.52	10.620%	$20.4868	$20.49	$20.50	$20.50
Purchase #5	$228.30	7.668%	$245.806	$245.81	$245.80	$245.80
Purchase #6	$131.52	7.838%	$141.8285	$141.83	$141.85	$141.80
Purchase #7	$222.45	8.256%	$240.8155	$240.82	$240.80	$240.80
7 purchase totals =	$1,028.54		$1,105.3457	$1,105.36	$1,105.35	$1,105.40