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	$145.66	10.855%	$161.4714	$161.47	$161.45	$161.50
Purchase #2	$131.96	9.153%	$144.0383	$144.04	$144.05	$144.00
Purchase #3	$18.46	13.151%	$20.8877	$20.89	$20.90	$20.90
Purchase #4	$94.85	8.137%	$102.5679	$102.57	$102.55	$102.60
Purchase #5	$220.69	9.780%	$242.2735	$242.27	$242.25	$242.30
Purchase #6	$175.79	7.204%	$188.4539	$188.45	$188.45	$188.50
Purchase #7	$233.39	9.542%	$255.6601	$255.66	$255.65	$255.70
7 purchase totals =	$1,020.80		$1,115.3528	$1,115.35	$1,115.30	$1,115.50