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	$100.78	4.522%	$105.3373	$105.34	$105.35	$105.30
Purchase #2	$220.52	13.148%	$249.514	$249.51	$249.50	$249.50
Purchase #3	$166.36	12.689%	$187.4694	$187.47	$187.45	$187.50
Purchase #4	$16.98	9.184%	$18.5394	$18.54	$18.55	$18.50
Purchase #5	$241.96	9.661%	$265.3358	$265.34	$265.35	$265.30
Purchase #6	$65.85	11.300%	$73.2911	$73.29	$73.30	$73.30
Purchase #7	$166.62	11.644%	$186.0212	$186.02	$186.00	$186.00
7 purchase totals =	$979.07		$1,085.5082	$1,085.51	$1,085.50	$1,085.40