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	$97.35	5.349%	$102.5573	$102.56	$102.55	$102.60
Purchase #2	$185.44	7.526%	$199.3962	$199.40	$199.40	$199.40
Purchase #3	$238.98	7.133%	$256.0264	$256.03	$256.05	$256.00
Purchase #4	$114.43	4.435%	$119.505	$119.51	$119.50	$119.50
Purchase #5	$108.82	10.493%	$120.2385	$120.24	$120.25	$120.20
Purchase #6	$37.34	3.740%	$38.7365	$38.74	$38.75	$38.70
Purchase #7	$236.81	5.751%	$250.4289	$250.43	$250.45	$250.40
7 purchase totals =	$1,019.17		$1,086.8888	$1,086.91	$1,086.95	$1,086.80