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	$185.79	10.645%	$205.5673	$205.57	$205.55	$205.60
Purchase #2	$107.30	8.257%	$116.1598	$116.16	$116.15	$116.20
Purchase #3	$94.61	12.146%	$106.1013	$106.10	$106.10	$106.10
Purchase #4	$196.92	11.155%	$218.8864	$218.89	$218.90	$218.90
Purchase #5	$71.61	10.226%	$78.9328	$78.93	$78.95	$78.90
Purchase #6	$181.98	8.807%	$198.007	$198.01	$198.00	$198.00
Purchase #7	$81.89	10.253%	$90.2862	$90.29	$90.30	$90.30
7 purchase totals =	$920.10		$1,013.9408	$1,013.95	$1,013.95	$1,014.00