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	$132.33	7.372%	$142.0854	$142.09	$142.10	$142.10
Purchase #2	$249.85	13.102%	$282.5853	$282.59	$282.60	$282.60
Purchase #3	$147.29	13.584%	$167.2979	$167.30	$167.30	$167.30
Purchase #4	$167.41	4.371%	$174.7275	$174.73	$174.75	$174.70
Purchase #5	$161.37	4.433%	$168.5235	$168.52	$168.50	$168.50
Purchase #6	$16.39	10.110%	$18.047	$18.05	$18.05	$18.00
Purchase #7	$233.76	9.841%	$256.7643	$256.76	$256.75	$256.80
7 purchase totals =	$1,108.40		$1,210.0309	$1,210.04	$1,210.05	$1,210.00