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	$68.62	13.740%	$78.0484	$78.05	$78.05	$78.00
Purchase #2	$30.46	3.593%	$31.5544	$31.55	$31.55	$31.60
Purchase #3	$205.85	13.733%	$234.1194	$234.12	$234.10	$234.10
Purchase #4	$181.27	5.401%	$191.0604	$191.06	$191.05	$191.10
Purchase #5	$83.35	3.429%	$86.2081	$86.21	$86.20	$86.20
Purchase #6	$179.62	10.768%	$198.9615	$198.96	$198.95	$199.00
Purchase #7	$191.56	10.598%	$211.8615	$211.86	$211.85	$211.90
7 purchase totals =	$940.73		$1,031.8137	$1,031.81	$1,031.75	$1,031.90