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	$90.37	9.401%	$98.8657	$98.87	$98.85	$98.90
Purchase #2	$101.42	7.598%	$109.1259	$109.13	$109.15	$109.10
Purchase #3	$164.59	7.502%	$176.9375	$176.94	$176.95	$176.90
Purchase #4	$30.69	10.312%	$33.8548	$33.85	$33.85	$33.90
Purchase #5	$153.28	9.532%	$167.8906	$167.89	$167.90	$167.90
Purchase #6	$185.34	6.260%	$196.9423	$196.94	$196.95	$196.90
Purchase #7	$201.53	11.867%	$225.4456	$225.45	$225.45	$225.40
7 purchase totals =	$927.22		$1,009.0624	$1,009.07	$1,009.10	$1,009.00