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	$82.25	5.650%	$86.8971	$86.90	$86.90	$86.90
Purchase #2	$212.57	13.559%	$241.3924	$241.39	$241.40	$241.40
Purchase #3	$164.70	9.608%	$180.5244	$180.52	$180.50	$180.50
Purchase #4	$92.81	3.551%	$96.1057	$96.11	$96.10	$96.10
Purchase #5	$86.26	3.856%	$89.5862	$89.59	$89.60	$89.60
Purchase #6	$140.46	8.347%	$152.1842	$152.18	$152.20	$152.20
Purchase #7	$229.59	12.719%	$258.7916	$258.79	$258.80	$258.80
7 purchase totals =	$1,008.64		$1,105.4816	$1,105.48	$1,105.50	$1,105.50