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	$245.43	8.637%	$266.6278	$266.63	$266.65	$266.60
Purchase #2	$31.84	12.659%	$35.8706	$35.87	$35.85	$35.90
Purchase #3	$200.42	9.300%	$219.0591	$219.06	$219.05	$219.10
Purchase #4	$117.70	7.352%	$126.3533	$126.35	$126.35	$126.40
Purchase #5	$177.89	4.169%	$185.3062	$185.31	$185.30	$185.30
Purchase #6	$120.94	5.311%	$127.3631	$127.36	$127.35	$127.40
Purchase #7	$61.74	6.504%	$65.7556	$65.76	$65.75	$65.80
7 purchase totals =	$955.96		$1,026.3357	$1,026.34	$1,026.30	$1,026.50