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	$104.96	6.541%	$111.8254	$111.83	$111.85	$111.80
Purchase #2	$168.50	7.365%	$180.91	$180.91	$180.90	$180.90
Purchase #3	$26.62	3.524%	$27.5581	$27.56	$27.55	$27.60
Purchase #4	$84.66	6.820%	$90.4338	$90.43	$90.45	$90.40
Purchase #5	$210.59	3.279%	$217.4952	$217.50	$217.50	$217.50
Purchase #6	$41.49	7.421%	$44.569	$44.57	$44.55	$44.60
Purchase #7	$162.75	13.400%	$184.5585	$184.56	$184.55	$184.60
7 purchase totals =	$799.57		$857.3500	$857.36	$857.35	$857.40