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	$139.64	3.449%	$144.4562	$144.46	$144.45	$144.50
Purchase #2	$86.45	10.268%	$95.3267	$95.33	$95.35	$95.30
Purchase #3	$159.30	4.833%	$166.999	$167.00	$167.00	$167.00
Purchase #4	$178.39	10.265%	$196.7017	$196.70	$196.70	$196.70
Purchase #5	$163.89	5.152%	$172.3336	$172.33	$172.35	$172.30
Purchase #6	$210.89	12.374%	$236.9855	$236.99	$237.00	$237.00
Purchase #7	$168.41	6.543%	$179.4291	$179.43	$179.45	$179.40
7 purchase totals =	$1,106.97		$1,192.2318	$1,192.24	$1,192.30	$1,192.20