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	$9.66	10.263%	$10.6514	$10.65	$10.65	$10.70
Purchase #2	$225.78	10.522%	$249.5366	$249.54	$249.55	$249.50
Purchase #3	$141.25	6.489%	$150.4157	$150.42	$150.40	$150.40
Purchase #4	$32.40	5.132%	$34.0628	$34.06	$34.05	$34.10
Purchase #5	$176.78	3.259%	$182.5413	$182.54	$182.55	$182.50
Purchase #6	$191.27	13.740%	$217.5505	$217.55	$217.55	$217.60
Purchase #7	$236.95	7.790%	$255.4084	$255.41	$255.40	$255.40
7 purchase totals =	$1,014.09		$1,100.1667	$1,100.17	$1,100.15	$1,100.20