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	$197.32	4.672%	$206.5388	$206.54	$206.55	$206.50
Purchase #2	$133.44	6.597%	$142.243	$142.24	$142.25	$142.20
Purchase #3	$102.38	12.169%	$114.8386	$114.84	$114.85	$114.80
Purchase #4	$72.58	7.129%	$77.7542	$77.75	$77.75	$77.80
Purchase #5	$36.49	9.857%	$40.0868	$40.09	$40.10	$40.10
Purchase #6	$156.38	10.548%	$172.875	$172.88	$172.90	$172.90
Purchase #7	$6.94	13.554%	$7.8806	$7.88	$7.90	$7.90
7 purchase totals =	$705.53		$762.2170	$762.22	$762.30	$762.20