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	$149.83	9.554%	$164.1448	$164.14	$164.15	$164.10
Purchase #2	$148.64	12.867%	$167.7655	$167.77	$167.75	$167.80
Purchase #3	$7.65	3.276%	$7.9006	$7.90	$7.90	$7.90
Purchase #4	$145.34	13.423%	$164.849	$164.85	$164.85	$164.80
Purchase #5	$42.61	4.558%	$44.5522	$44.55	$44.55	$44.60
Purchase #6	$185.35	5.511%	$195.5646	$195.56	$195.55	$195.60
Purchase #7	$30.52	10.238%	$33.6446	$33.64	$33.65	$33.60
7 purchase totals =	$709.94		$778.4213	$778.41	$778.40	$778.40