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	$198.48	13.190%	$224.6595	$224.66	$224.65	$224.70
Purchase #2	$104.31	11.665%	$116.4778	$116.48	$116.50	$116.50
Purchase #3	$236.98	5.237%	$249.3906	$249.39	$249.40	$249.40
Purchase #4	$25.86	6.105%	$27.4388	$27.44	$27.45	$27.40
Purchase #5	$121.53	4.465%	$126.9563	$126.96	$126.95	$127.00
Purchase #6	$145.93	3.131%	$150.4991	$150.50	$150.50	$150.50
Purchase #7	$51.56	3.767%	$53.5023	$53.50	$53.50	$53.50
7 purchase totals =	$884.65		$948.9244	$948.93	$948.95	$949.00