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	$196.35	12.144%	$220.1947	$220.19	$220.20	$220.20
Purchase #2	$76.35	9.164%	$83.3467	$83.35	$83.35	$83.30
Purchase #3	$172.50	5.276%	$181.6011	$181.60	$181.60	$181.60
Purchase #4	$174.73	12.673%	$196.8735	$196.87	$196.85	$196.90
Purchase #5	$136.83	4.346%	$142.7766	$142.78	$142.80	$142.80
Purchase #6	$72.50	10.482%	$80.0995	$80.10	$80.10	$80.10
Purchase #7	$194.64	6.632%	$207.5485	$207.55	$207.55	$207.50
7 purchase totals =	$1,023.90		$1,112.4406	$1,112.44	$1,112.45	$1,112.40