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	$157.65	3.246%	$162.7673	$162.77	$162.75	$162.80
Purchase #2	$40.91	10.158%	$45.0656	$45.07	$45.05	$45.10
Purchase #3	$178.45	10.209%	$196.668	$196.67	$196.65	$196.70
Purchase #4	$185.65	5.228%	$195.3558	$195.36	$195.35	$195.40
Purchase #5	$41.76	12.386%	$46.9324	$46.93	$46.95	$46.90
Purchase #6	$129.46	7.684%	$139.4077	$139.41	$139.40	$139.40
Purchase #7	$222.74	7.286%	$238.9688	$238.97	$238.95	$239.00
7 purchase totals =	$956.62		$1,025.1656	$1,025.18	$1,025.10	$1,025.30