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	$37.41	10.225%	$41.2352	$41.24	$41.25	$41.20
Purchase #2	$237.42	13.766%	$270.1032	$270.10	$270.10	$270.10
Purchase #3	$100.77	6.243%	$107.0611	$107.06	$107.05	$107.10
Purchase #4	$81.56	4.849%	$85.5148	$85.51	$85.50	$85.50
Purchase #5	$243.83	13.194%	$276.0009	$276.00	$276.00	$276.00
Purchase #6	$10.76	4.650%	$11.2603	$11.26	$11.25	$11.30
Purchase #7	$249.65	12.524%	$280.9162	$280.92	$280.90	$280.90
7 purchase totals =	$961.40		$1,072.0917	$1,072.09	$1,072.05	$1,072.10