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	$144.32	7.661%	$155.3764	$155.38	$155.40	$155.40
Purchase #2	$145.56	3.555%	$150.7347	$150.73	$150.75	$150.70
Purchase #3	$120.74	9.557%	$132.2791	$132.28	$132.30	$132.30
Purchase #4	$113.42	3.709%	$117.6267	$117.63	$117.65	$117.60
Purchase #5	$21.38	7.268%	$22.9339	$22.93	$22.95	$22.90
Purchase #6	$68.73	5.385%	$72.4311	$72.43	$72.45	$72.40
Purchase #7	$148.73	3.216%	$153.5132	$153.51	$153.50	$153.50
7 purchase totals =	$762.88		$804.8951	$804.89	$805.00	$804.80