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	$152.59	7.183%	$163.5505	$163.55	$163.55	$163.60
Purchase #2	$200.25	12.463%	$225.2072	$225.21	$225.20	$225.20
Purchase #3	$51.64	7.377%	$55.4495	$55.45	$55.45	$55.40
Purchase #4	$56.54	6.601%	$60.2722	$60.27	$60.25	$60.30
Purchase #5	$49.61	13.522%	$56.3183	$56.32	$56.30	$56.30
Purchase #6	$165.25	9.309%	$180.6331	$180.63	$180.65	$180.60
Purchase #7	$82.38	3.737%	$85.4585	$85.46	$85.45	$85.50
7 purchase totals =	$758.26		$826.8893	$826.89	$826.85	$826.90