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	$43.98	3.518%	$45.5272	$45.53	$45.55	$45.50
Purchase #2	$45.42	11.462%	$50.626	$50.63	$50.65	$50.60
Purchase #3	$98.88	5.232%	$104.0534	$104.05	$104.05	$104.10
Purchase #4	$81.33	7.189%	$87.1768	$87.18	$87.20	$87.20
Purchase #5	$173.28	13.305%	$196.3349	$196.33	$196.35	$196.30
Purchase #6	$17.54	8.123%	$18.9648	$18.96	$18.95	$19.00
Purchase #7	$167.33	8.714%	$181.9111	$181.91	$181.90	$181.90
7 purchase totals =	$627.76		$684.5942	$684.59	$684.65	$684.60