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	$36.66	3.547%	$37.9603	$37.96	$37.95	$38.00
Purchase #2	$114.41	3.854%	$118.8194	$118.82	$118.80	$118.80
Purchase #3	$105.44	11.261%	$117.3136	$117.31	$117.30	$117.30
Purchase #4	$243.43	6.506%	$259.2676	$259.27	$259.25	$259.30
Purchase #5	$194.53	12.366%	$218.5856	$218.59	$218.60	$218.60
Purchase #6	$191.70	8.770%	$208.5121	$208.51	$208.50	$208.50
Purchase #7	$90.61	6.448%	$96.4525	$96.45	$96.45	$96.50
7 purchase totals =	$976.78		$1,056.9111	$1,056.91	$1,056.85	$1,057.00