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	$186.98	10.331%	$206.2969	$206.30	$206.30	$206.30
Purchase #2	$153.54	10.233%	$169.2517	$169.25	$169.25	$169.30
Purchase #3	$206.57	3.746%	$214.3081	$214.31	$214.30	$214.30
Purchase #4	$86.63	3.419%	$89.5919	$89.59	$89.60	$89.60
Purchase #5	$234.41	6.215%	$248.9786	$248.98	$249.00	$249.00
Purchase #6	$109.72	3.698%	$113.7774	$113.78	$113.80	$113.80
Purchase #7	$16.93	10.759%	$18.7515	$18.75	$18.75	$18.80
7 purchase totals =	$994.78		$1,060.9561	$1,060.96	$1,061.00	$1,061.10