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	$157.50	7.244%	$168.9093	$168.91	$168.90	$168.90
Purchase #2	$208.67	9.384%	$228.2516	$228.25	$228.25	$228.30
Purchase #3	$21.44	4.623%	$22.4312	$22.43	$22.45	$22.40
Purchase #4	$70.33	11.819%	$78.6423	$78.64	$78.65	$78.60
Purchase #5	$216.37	4.322%	$225.7215	$225.72	$225.70	$225.70
Purchase #6	$119.93	3.352%	$123.9501	$123.95	$123.95	$124.00
Purchase #7	$145.90	7.867%	$157.378	$157.38	$157.40	$157.40
7 purchase totals =	$940.14		$1,005.2840	$1,005.28	$1,005.30	$1,005.30