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	$131.90	10.188%	$145.338	$145.34	$145.35	$145.30
Purchase #2	$37.63	10.307%	$41.5085	$41.51	$41.50	$41.50
Purchase #3	$249.47	10.769%	$276.3354	$276.34	$276.35	$276.30
Purchase #4	$159.30	9.253%	$174.04	$174.04	$174.05	$174.00
Purchase #5	$139.90	7.594%	$150.524	$150.52	$150.50	$150.50
Purchase #6	$47.31	8.760%	$51.4544	$51.45	$51.45	$51.50
Purchase #7	$8.56	3.155%	$8.8301	$8.83	$8.85	$8.80
7 purchase totals =	$774.07		$848.0304	$848.03	$848.05	$847.90