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	$187.43	12.526%	$210.9075	$210.91	$210.90	$210.90
Purchase #2	$67.78	9.589%	$74.2794	$74.28	$74.30	$74.30
Purchase #3	$64.42	12.492%	$72.4673	$72.47	$72.45	$72.50
Purchase #4	$156.54	9.800%	$171.8809	$171.88	$171.90	$171.90
Purchase #5	$104.73	3.137%	$108.0154	$108.02	$108.00	$108.00
Purchase #6	$226.58	11.815%	$253.3504	$253.35	$253.35	$253.40
Purchase #7	$182.82	6.717%	$195.1	$195.10	$195.10	$195.10
7 purchase totals =	$990.30		$1,086.0009	$1,086.01	$1,086.00	$1,086.10