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	$102.41	4.426%	$106.9427	$106.94	$106.95	$106.90
Purchase #2	$202.88	10.191%	$223.5555	$223.56	$223.55	$223.60
Purchase #3	$206.38	7.716%	$222.3043	$222.30	$222.30	$222.30
Purchase #4	$226.61	9.766%	$248.7407	$248.74	$248.75	$248.70
Purchase #5	$59.36	13.665%	$67.4715	$67.47	$67.45	$67.50
Purchase #6	$164.38	11.284%	$182.9286	$182.93	$182.95	$182.90
Purchase #7	$226.99	9.686%	$248.9763	$248.98	$249.00	$249.00
7 purchase totals =	$1,189.01		$1,300.9196	$1,300.92	$1,300.95	$1,300.90