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	$56.65	4.298%	$59.0848	$59.08	$59.10	$59.10
Purchase #2	$118.87	4.504%	$124.2239	$124.22	$124.20	$124.20
Purchase #3	$210.98	7.287%	$226.3541	$226.35	$226.35	$226.40
Purchase #4	$222.46	9.427%	$243.4313	$243.43	$243.45	$243.40
Purchase #5	$72.51	7.641%	$78.0505	$78.05	$78.05	$78.10
Purchase #6	$7.53	13.385%	$8.5379	$8.54	$8.55	$8.50
Purchase #7	$184.89	12.425%	$207.8626	$207.86	$207.85	$207.90
7 purchase totals =	$873.89		$947.5451	$947.53	$947.55	$947.60