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	$95.65	3.835%	$99.3182	$99.32	$99.30	$99.30
Purchase #2	$233.47	5.560%	$246.4509	$246.45	$246.45	$246.50
Purchase #3	$142.44	12.189%	$159.802	$159.80	$159.80	$159.80
Purchase #4	$194.79	9.309%	$212.923	$212.92	$212.90	$212.90
Purchase #5	$114.25	4.642%	$119.5535	$119.55	$119.55	$119.60
Purchase #6	$197.39	9.640%	$216.4184	$216.42	$216.40	$216.40
Purchase #7	$28.74	13.321%	$32.5685	$32.57	$32.55	$32.60
7 purchase totals =	$1,006.73		$1,087.0345	$1,087.03	$1,086.95	$1,087.10