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	$97.27	6.384%	$103.4797	$103.48	$103.50	$103.50
Purchase #2	$161.60	8.558%	$175.4297	$175.43	$175.45	$175.40
Purchase #3	$202.89	3.280%	$209.5448	$209.54	$209.55	$209.50
Purchase #4	$163.76	11.366%	$182.373	$182.37	$182.35	$182.40
Purchase #5	$103.77	11.770%	$115.9837	$115.98	$116.00	$116.00
Purchase #6	$131.62	6.145%	$139.708	$139.71	$139.70	$139.70
Purchase #7	$135.95	10.427%	$150.1255	$150.13	$150.15	$150.10
7 purchase totals =	$996.86		$1,076.6444	$1,076.64	$1,076.70	$1,076.60