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	$127.68	11.340%	$142.1589	$142.16	$142.15	$142.20
Purchase #2	$73.70	9.831%	$80.9454	$80.95	$80.95	$80.90
Purchase #3	$97.88	5.851%	$103.607	$103.61	$103.60	$103.60
Purchase #4	$247.65	4.642%	$259.1459	$259.15	$259.15	$259.10
Purchase #5	$97.95	11.873%	$109.5796	$109.58	$109.60	$109.60
Purchase #6	$41.40	13.334%	$46.9203	$46.92	$46.90	$46.90
Purchase #7	$69.42	12.781%	$78.2926	$78.29	$78.30	$78.30
7 purchase totals =	$755.68		$820.6497	$820.66	$820.65	$820.60