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	$175.38	9.422%	$191.9043	$191.90	$191.90	$191.90
Purchase #2	$157.83	7.366%	$169.4558	$169.46	$169.45	$169.50
Purchase #3	$100.97	9.661%	$110.7247	$110.72	$110.70	$110.70
Purchase #4	$128.42	10.559%	$141.9799	$141.98	$142.00	$142.00
Purchase #5	$114.41	5.674%	$120.9016	$120.90	$120.90	$120.90
Purchase #6	$162.94	12.236%	$182.8773	$182.88	$182.90	$182.90
Purchase #7	$105.55	7.835%	$113.8198	$113.82	$113.80	$113.80
7 purchase totals =	$945.50		$1,031.6634	$1,031.66	$1,031.65	$1,031.70