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	$144.45	5.604%	$152.545	$152.55	$152.55	$152.50
Purchase #2	$85.81	11.114%	$95.3469	$95.35	$95.35	$95.30
Purchase #3	$129.28	8.567%	$140.3554	$140.36	$140.35	$140.40
Purchase #4	$29.86	4.556%	$31.2204	$31.22	$31.20	$31.20
Purchase #5	$198.99	10.469%	$219.8223	$219.82	$219.80	$219.80
Purchase #6	$35.68	5.153%	$37.5186	$37.52	$37.50	$37.50
Purchase #7	$179.80	10.438%	$198.5675	$198.57	$198.55	$198.60
7 purchase totals =	$803.87		$875.3761	$875.39	$875.30	$875.30