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	$97.84	4.540%	$102.2819	$102.28	$102.30	$102.30
Purchase #2	$170.55	9.327%	$186.4572	$186.46	$186.45	$186.50
Purchase #3	$49.46	13.441%	$56.1079	$56.11	$56.10	$56.10
Purchase #4	$99.53	9.249%	$108.7355	$108.74	$108.75	$108.70
Purchase #5	$113.89	11.722%	$127.2402	$127.24	$127.25	$127.20
Purchase #6	$250.42	10.208%	$275.9829	$275.98	$276.00	$276.00
Purchase #7	$84.32	12.674%	$95.0067	$95.01	$95.00	$95.00
7 purchase totals =	$866.01		$951.8123	$951.82	$951.85	$951.80