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	$117.80	11.445%	$131.2822	$131.28	$131.30	$131.30
Purchase #2	$37.65	7.266%	$40.3856	$40.39	$40.40	$40.40
Purchase #3	$117.48	7.649%	$126.466	$126.47	$126.45	$126.50
Purchase #4	$66.78	6.452%	$71.0886	$71.09	$71.10	$71.10
Purchase #5	$226.81	12.223%	$254.533	$254.53	$254.55	$254.50
Purchase #6	$26.33	6.399%	$28.0149	$28.01	$28.00	$28.00
Purchase #7	$106.33	7.302%	$114.0942	$114.09	$114.10	$114.10
7 purchase totals =	$699.18		$765.8645	$765.86	$765.90	$765.90