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	$102.57	7.184%	$109.9386	$109.94	$109.95	$109.90
Purchase #2	$109.33	12.618%	$123.1253	$123.13	$123.15	$123.10
Purchase #3	$52.64	4.662%	$55.0941	$55.09	$55.10	$55.10
Purchase #4	$89.50	7.792%	$96.4738	$96.47	$96.45	$96.50
Purchase #5	$99.91	3.363%	$103.27	$103.27	$103.25	$103.30
Purchase #6	$41.25	6.671%	$44.0018	$44.00	$44.00	$44.00
Purchase #7	$67.30	3.681%	$69.7773	$69.78	$69.80	$69.80
7 purchase totals =	$562.50		$601.6809	$601.68	$601.70	$601.70