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	$140.25	11.342%	$156.1572	$156.16	$156.15	$156.20
Purchase #2	$240.55	9.198%	$262.6758	$262.68	$262.70	$262.70
Purchase #3	$85.49	8.132%	$92.442	$92.44	$92.45	$92.40
Purchase #4	$162.30	7.761%	$174.8961	$174.90	$174.90	$174.90
Purchase #5	$152.69	11.561%	$170.3425	$170.34	$170.35	$170.30
Purchase #6	$168.39	3.671%	$174.5716	$174.57	$174.55	$174.60
Purchase #7	$42.65	5.686%	$45.0751	$45.08	$45.10	$45.10
7 purchase totals =	$992.32		$1,076.1603	$1,076.17	$1,076.20	$1,076.20