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	$91.63	10.359%	$101.122	$101.12	$101.10	$101.10
Purchase #2	$41.91	9.144%	$45.7423	$45.74	$45.75	$45.70
Purchase #3	$138.48	12.805%	$156.2124	$156.21	$156.20	$156.20
Purchase #4	$85.66	5.814%	$90.6403	$90.64	$90.65	$90.60
Purchase #5	$236.31	7.696%	$254.4964	$254.50	$254.50	$254.50
Purchase #6	$146.82	4.455%	$153.3608	$153.36	$153.35	$153.40
Purchase #7	$246.72	6.461%	$262.6606	$262.66	$262.65	$262.70
7 purchase totals =	$987.53		$1,064.2348	$1,064.23	$1,064.20	$1,064.20