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	$88.26	11.681%	$98.5697	$98.57	$98.55	$98.60
Purchase #2	$146.79	10.599%	$162.3483	$162.35	$162.35	$162.30
Purchase #3	$173.36	8.764%	$188.5533	$188.55	$188.55	$188.60
Purchase #4	$9.46	3.584%	$9.799	$9.80	$9.80	$9.80
Purchase #5	$168.57	12.425%	$189.5148	$189.51	$189.50	$189.50
Purchase #6	$217.72	9.351%	$238.079	$238.08	$238.10	$238.10
Purchase #7	$186.39	5.474%	$196.593	$196.59	$196.60	$196.60
7 purchase totals =	$990.55		$1,083.4571	$1,083.45	$1,083.45	$1,083.50