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	$114.51	11.245%	$127.3866	$127.39	$127.40	$127.40
Purchase #2	$200.28	12.349%	$225.0126	$225.01	$225.00	$225.00
Purchase #3	$250.52	11.623%	$279.6379	$279.64	$279.65	$279.60
Purchase #4	$168.97	9.537%	$185.0847	$185.08	$185.10	$185.10
Purchase #5	$210.34	8.271%	$227.7372	$227.74	$227.75	$227.70
Purchase #6	$250.50	6.755%	$267.4213	$267.42	$267.40	$267.40
Purchase #7	$66.77	6.303%	$70.9785	$70.98	$71.00	$71.00
7 purchase totals =	$1,261.89		$1,383.2588	$1,383.26	$1,383.30	$1,383.20