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	$129.82	4.859%	$136.128	$136.13	$136.15	$136.10
Purchase #2	$16.26	11.213%	$18.0832	$18.08	$18.10	$18.10
Purchase #3	$76.88	3.596%	$79.6446	$79.64	$79.65	$79.60
Purchase #4	$101.42	13.330%	$114.9393	$114.94	$114.95	$114.90
Purchase #5	$37.87	12.158%	$42.4742	$42.47	$42.45	$42.50
Purchase #6	$153.45	4.221%	$159.9271	$159.93	$159.95	$159.90
Purchase #7	$91.91	9.702%	$100.8271	$100.83	$100.85	$100.80
7 purchase totals =	$607.61		$652.0235	$652.02	$652.10	$651.90