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	$59.51	6.360%	$63.2948	$63.29	$63.30	$63.30
Purchase #2	$63.69	6.112%	$67.5827	$67.58	$67.60	$67.60
Purchase #3	$237.49	11.381%	$264.5187	$264.52	$264.50	$264.50
Purchase #4	$29.34	6.569%	$31.2673	$31.27	$31.25	$31.30
Purchase #5	$181.79	3.153%	$187.5218	$187.52	$187.50	$187.50
Purchase #6	$184.46	3.580%	$191.0637	$191.06	$191.05	$191.10
Purchase #7	$56.47	9.371%	$61.7618	$61.76	$61.75	$61.80
7 purchase totals =	$812.75		$867.0108	$867.00	$866.95	$867.10