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	$115.83	10.226%	$127.6748	$127.67	$127.65	$127.70
Purchase #2	$61.94	9.779%	$67.9971	$68.00	$68.00	$68.00
Purchase #3	$231.92	4.502%	$242.361	$242.36	$242.35	$242.40
Purchase #4	$80.91	11.839%	$90.4889	$90.49	$90.50	$90.50
Purchase #5	$134.57	5.432%	$141.8798	$141.88	$141.90	$141.90
Purchase #6	$150.38	8.166%	$162.66	$162.66	$162.65	$162.70
Purchase #7	$156.74	5.868%	$165.9375	$165.94	$165.95	$165.90
7 purchase totals =	$932.29		$998.9991	$999.00	$999.00	$999.10