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	$236.56	13.456%	$268.3915	$268.39	$268.40	$268.40
Purchase #2	$81.40	5.553%	$85.9201	$85.92	$85.90	$85.90
Purchase #3	$78.51	7.192%	$84.1564	$84.16	$84.15	$84.20
Purchase #4	$103.89	4.200%	$108.2534	$108.25	$108.25	$108.30
Purchase #5	$228.77	7.131%	$245.0836	$245.08	$245.10	$245.10
Purchase #6	$189.81	12.359%	$213.2686	$213.27	$213.25	$213.30
Purchase #7	$114.63	11.453%	$127.7586	$127.76	$127.75	$127.80
7 purchase totals =	$1,033.57		$1,132.8322	$1,132.83	$1,132.80	$1,133.00