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	$142.97	12.254%	$160.4895	$160.49	$160.50	$160.50
Purchase #2	$66.31	9.423%	$72.5584	$72.56	$72.55	$72.60
Purchase #3	$74.43	9.722%	$81.6661	$81.67	$81.65	$81.70
Purchase #4	$242.51	13.802%	$275.9812	$275.98	$276.00	$276.00
Purchase #5	$52.75	3.603%	$54.6506	$54.65	$54.65	$54.70
Purchase #6	$245.88	13.477%	$279.0172	$279.02	$279.00	$279.00
Purchase #7	$81.99	9.529%	$89.8028	$89.80	$89.80	$89.80
7 purchase totals =	$906.84		$1,014.1658	$1,014.17	$1,014.15	$1,014.30