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	$218.85	4.430%	$228.5451	$228.55	$228.55	$228.50
Purchase #2	$34.69	7.258%	$37.2078	$37.21	$37.20	$37.20
Purchase #3	$113.48	6.511%	$120.8687	$120.87	$120.85	$120.90
Purchase #4	$38.49	4.502%	$40.2228	$40.22	$40.20	$40.20
Purchase #5	$56.82	10.107%	$62.5628	$62.56	$62.55	$62.60
Purchase #6	$126.49	12.244%	$141.9774	$141.98	$142.00	$142.00
Purchase #7	$115.86	6.234%	$123.0827	$123.08	$123.10	$123.10
7 purchase totals =	$704.68		$754.4673	$754.47	$754.45	$754.50