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	$84.63	5.300%	$89.1154	$89.12	$89.10	$89.10
Purchase #2	$125.85	10.708%	$139.326	$139.33	$139.35	$139.30
Purchase #3	$187.42	3.479%	$193.9403	$193.94	$193.95	$193.90
Purchase #4	$224.40	12.127%	$251.613	$251.61	$251.60	$251.60
Purchase #5	$200.50	5.791%	$212.111	$212.11	$212.10	$212.10
Purchase #6	$52.74	13.855%	$60.0471	$60.05	$60.05	$60.00
Purchase #7	$56.91	8.689%	$61.8549	$61.85	$61.85	$61.90
7 purchase totals =	$932.45		$1,008.0077	$1,008.01	$1,008.00	$1,007.90