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	$133.94	12.533%	$150.7267	$150.73	$150.75	$150.70
Purchase #2	$47.80	7.284%	$51.2818	$51.28	$51.30	$51.30
Purchase #3	$112.45	10.523%	$124.2831	$124.28	$124.30	$124.30
Purchase #4	$16.42	5.831%	$17.3775	$17.38	$17.40	$17.40
Purchase #5	$179.52	3.480%	$185.7673	$185.77	$185.75	$185.80
Purchase #6	$146.33	3.369%	$151.2599	$151.26	$151.25	$151.30
Purchase #7	$182.67	7.514%	$196.3958	$196.40	$196.40	$196.40
7 purchase totals =	$819.13		$877.0921	$877.10	$877.15	$877.20