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	$222.62	9.180%	$243.0565	$243.06	$243.05	$243.10
Purchase #2	$134.40	11.868%	$150.3506	$150.35	$150.35	$150.40
Purchase #3	$247.92	5.538%	$261.6498	$261.65	$261.65	$261.60
Purchase #4	$80.76	6.214%	$85.7784	$85.78	$85.80	$85.80
Purchase #5	$119.32	6.714%	$127.3311	$127.33	$127.35	$127.30
Purchase #6	$110.66	7.626%	$119.0989	$119.10	$119.10	$119.10
Purchase #7	$15.45	11.673%	$17.2535	$17.25	$17.25	$17.30
7 purchase totals =	$931.13		$1,004.5188	$1,004.52	$1,004.55	$1,004.60