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	$161.42	5.164%	$169.7557	$169.76	$169.75	$169.80
Purchase #2	$47.92	12.865%	$54.0849	$54.08	$54.10	$54.10
Purchase #3	$172.35	3.844%	$178.9751	$178.98	$179.00	$179.00
Purchase #4	$224.38	13.659%	$255.0281	$255.03	$255.05	$255.00
Purchase #5	$59.93	8.278%	$64.891	$64.89	$64.90	$64.90
Purchase #6	$153.39	13.451%	$174.0225	$174.02	$174.00	$174.00
Purchase #7	$221.76	12.779%	$250.0987	$250.10	$250.10	$250.10
7 purchase totals =	$1,041.15		$1,146.8560	$1,146.86	$1,146.90	$1,146.90