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	$162.98	6.494%	$173.5639	$173.56	$173.55	$173.60
Purchase #2	$179.79	7.683%	$193.6033	$193.60	$193.60	$193.60
Purchase #3	$29.66	12.804%	$33.4577	$33.46	$33.45	$33.50
Purchase #4	$237.72	6.244%	$252.5632	$252.56	$252.55	$252.60
Purchase #5	$206.33	13.696%	$234.589	$234.59	$234.60	$234.60
Purchase #6	$31.64	3.855%	$32.8597	$32.86	$32.85	$32.90
Purchase #7	$78.38	3.426%	$81.0653	$81.07	$81.05	$81.10
7 purchase totals =	$926.50		$1,001.7021	$1,001.70	$1,001.65	$1,001.90