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	$89.57	6.542%	$95.4297	$95.43	$95.45	$95.40
Purchase #2	$104.42	6.694%	$111.4099	$111.41	$111.40	$111.40
Purchase #3	$125.86	7.815%	$135.696	$135.70	$135.70	$135.70
Purchase #4	$198.74	11.702%	$221.9966	$222.00	$222.00	$222.00
Purchase #5	$74.53	10.765%	$82.5532	$82.55	$82.55	$82.60
Purchase #6	$129.43	12.643%	$145.7938	$145.79	$145.80	$145.80
Purchase #7	$84.32	5.769%	$89.1844	$89.18	$89.20	$89.20
7 purchase totals =	$806.87		$882.0636	$882.06	$882.10	$882.10