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	$187.51	4.558%	$196.0567	$196.06	$196.05	$196.10
Purchase #2	$22.72	13.639%	$25.8188	$25.82	$25.80	$25.80
Purchase #3	$17.28	5.215%	$18.1812	$18.18	$18.20	$18.20
Purchase #4	$216.42	6.779%	$231.0911	$231.09	$231.10	$231.10
Purchase #5	$138.77	12.109%	$155.5737	$155.57	$155.55	$155.60
Purchase #6	$90.78	7.713%	$97.7819	$97.78	$97.80	$97.80
Purchase #7	$226.74	10.818%	$251.2687	$251.27	$251.25	$251.30
7 purchase totals =	$900.22		$975.7721	$975.77	$975.75	$975.90