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	$82.65	4.627%	$86.4742	$86.47	$86.45	$86.50
Purchase #2	$91.76	9.769%	$100.724	$100.72	$100.70	$100.70
Purchase #3	$167.47	8.104%	$181.0418	$181.04	$181.05	$181.00
Purchase #4	$170.82	13.771%	$194.3436	$194.34	$194.35	$194.30
Purchase #5	$138.82	8.288%	$150.3254	$150.33	$150.35	$150.30
Purchase #6	$245.96	13.827%	$279.9689	$279.97	$279.95	$280.00
Purchase #7	$188.92	9.388%	$206.6558	$206.66	$206.65	$206.70
7 purchase totals =	$1,086.40		$1,199.5337	$1,199.53	$1,199.50	$1,199.50