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	$203.33	7.440%	$218.4578	$218.46	$218.45	$218.50
Purchase #2	$165.82	13.334%	$187.9304	$187.93	$187.95	$187.90
Purchase #3	$140.26	5.601%	$148.116	$148.12	$148.10	$148.10
Purchase #4	$57.58	11.806%	$64.3779	$64.38	$64.40	$64.40
Purchase #5	$174.29	7.223%	$186.879	$186.88	$186.90	$186.90
Purchase #6	$172.58	6.304%	$183.4594	$183.46	$183.45	$183.50
Purchase #7	$38.36	5.690%	$40.5427	$40.54	$40.55	$40.50
7 purchase totals =	$952.22		$1,029.7632	$1,029.77	$1,029.80	$1,029.80