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	$177.28	10.867%	$196.545	$196.55	$196.55	$196.50
Purchase #2	$169.59	12.731%	$191.1805	$191.18	$191.20	$191.20
Purchase #3	$137.79	5.746%	$145.7074	$145.71	$145.70	$145.70
Purchase #4	$93.31	10.555%	$103.1589	$103.16	$103.15	$103.20
Purchase #5	$240.29	11.871%	$268.8148	$268.81	$268.80	$268.80
Purchase #6	$27.52	6.482%	$29.3038	$29.30	$29.30	$29.30
Purchase #7	$58.95	11.685%	$65.8383	$65.84	$65.85	$65.80
7 purchase totals =	$904.73		$1,000.5487	$1,000.55	$1,000.55	$1,000.50