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	$102.36	13.367%	$116.0425	$116.04	$116.05	$116.00
Purchase #2	$60.26	6.513%	$64.1847	$64.18	$64.20	$64.20
Purchase #3	$51.32	9.480%	$56.1851	$56.19	$56.20	$56.20
Purchase #4	$237.72	4.284%	$247.9039	$247.90	$247.90	$247.90
Purchase #5	$104.38	6.640%	$111.3108	$111.31	$111.30	$111.30
Purchase #6	$40.45	4.210%	$42.1529	$42.15	$42.15	$42.20
Purchase #7	$97.50	6.731%	$104.0627	$104.06	$104.05	$104.10
7 purchase totals =	$693.99		$741.8426	$741.83	$741.85	$741.90