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	$65.68	9.314%	$71.7974	$71.80	$71.80	$71.80
Purchase #2	$162.88	7.603%	$175.2638	$175.26	$175.25	$175.30
Purchase #3	$145.37	13.362%	$164.7943	$164.79	$164.80	$164.80
Purchase #4	$151.35	13.202%	$171.3312	$171.33	$171.35	$171.30
Purchase #5	$224.82	3.110%	$231.8119	$231.81	$231.80	$231.80
Purchase #6	$103.96	3.421%	$107.5165	$107.52	$107.50	$107.50
Purchase #7	$162.67	7.477%	$174.8328	$174.83	$174.85	$174.80
7 purchase totals =	$1,016.73		$1,097.3479	$1,097.34	$1,097.35	$1,097.30