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	$237.34	4.686%	$248.4618	$248.46	$248.45	$248.50
Purchase #2	$237.55	12.752%	$267.8424	$267.84	$267.85	$267.80
Purchase #3	$57.25	6.773%	$61.1275	$61.13	$61.15	$61.10
Purchase #4	$175.40	4.273%	$182.8948	$182.89	$182.90	$182.90
Purchase #5	$113.88	10.677%	$126.039	$126.04	$126.05	$126.00
Purchase #6	$174.64	9.845%	$191.8333	$191.83	$191.85	$191.80
Purchase #7	$73.90	5.820%	$78.201	$78.20	$78.20	$78.20
7 purchase totals =	$1,069.96		$1,156.3998	$1,156.39	$1,156.45	$1,156.30