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	$233.63	13.199%	$264.4668	$264.47	$264.45	$264.50
Purchase #2	$10.88	7.214%	$11.6649	$11.66	$11.65	$11.70
Purchase #3	$94.48	9.306%	$103.2723	$103.27	$103.25	$103.30
Purchase #4	$38.40	11.650%	$42.8736	$42.87	$42.85	$42.90
Purchase #5	$51.33	4.280%	$53.5269	$53.53	$53.55	$53.50
Purchase #6	$37.88	7.738%	$40.8112	$40.81	$40.80	$40.80
Purchase #7	$186.26	6.655%	$198.6556	$198.66	$198.65	$198.70
7 purchase totals =	$652.86		$715.2713	$715.27	$715.20	$715.40