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	$182.77	4.315%	$190.6565	$190.66	$190.65	$190.70
Purchase #2	$117.53	11.490%	$131.0342	$131.03	$131.05	$131.00
Purchase #3	$156.82	5.821%	$165.9485	$165.95	$165.95	$165.90
Purchase #4	$74.27	13.830%	$84.5415	$84.54	$84.55	$84.50
Purchase #5	$14.54	5.331%	$15.3151	$15.32	$15.30	$15.30
Purchase #6	$95.59	11.328%	$106.4184	$106.42	$106.40	$106.40
Purchase #7	$122.77	4.244%	$127.9804	$127.98	$128.00	$128.00
7 purchase totals =	$764.29		$821.8946	$821.90	$821.90	$821.80