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	$68.48	4.350%	$71.4589	$71.46	$71.45	$71.50
Purchase #2	$100.52	13.319%	$113.9083	$113.91	$113.90	$113.90
Purchase #3	$113.42	12.753%	$127.8845	$127.88	$127.90	$127.90
Purchase #4	$51.88	6.788%	$55.4016	$55.40	$55.40	$55.40
Purchase #5	$211.80	3.151%	$218.4738	$218.47	$218.45	$218.50
Purchase #6	$204.54	11.418%	$227.8944	$227.89	$227.90	$227.90
Purchase #7	$38.58	12.823%	$43.5271	$43.53	$43.55	$43.50
7 purchase totals =	$789.22		$858.5486	$858.54	$858.55	$858.60