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	$80.67	10.150%	$88.858	$88.86	$88.85	$88.90
Purchase #2	$62.44	7.295%	$66.995	$67.00	$67.00	$67.00
Purchase #3	$81.68	7.768%	$88.0249	$88.02	$88.00	$88.00
Purchase #4	$69.67	4.655%	$72.9131	$72.91	$72.90	$72.90
Purchase #5	$5.76	10.441%	$6.3614	$6.36	$6.35	$6.40
Purchase #6	$32.30	13.181%	$36.5575	$36.56	$36.55	$36.60
Purchase #7	$79.59	12.496%	$89.5356	$89.54	$89.55	$89.50
7 purchase totals =	$412.11		$449.2455	$449.25	$449.20	$449.30