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	$86.36	6.851%	$92.2765	$92.28	$92.30	$92.30
Purchase #2	$72.66	8.849%	$79.0897	$79.09	$79.10	$79.10
Purchase #3	$66.92	8.706%	$72.7461	$72.75	$72.75	$72.70
Purchase #4	$37.56	3.264%	$38.786	$38.79	$38.80	$38.80
Purchase #5	$53.75	10.666%	$59.483	$59.48	$59.50	$59.50
Purchase #6	$50.29	4.363%	$52.4842	$52.48	$52.50	$52.50
Purchase #7	$47.39	13.457%	$53.7673	$53.77	$53.75	$53.80
7 purchase totals =	$414.93		$448.6328	$448.64	$448.70	$448.70