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	$163.58	7.765%	$176.282	$176.28	$176.30	$176.30
Purchase #2	$104.69	11.603%	$116.8372	$116.84	$116.85	$116.80
Purchase #3	$85.72	12.638%	$96.5533	$96.55	$96.55	$96.60
Purchase #4	$186.74	13.471%	$211.8957	$211.90	$211.90	$211.90
Purchase #5	$197.74	3.796%	$205.2462	$205.25	$205.25	$205.20
Purchase #6	$196.65	10.613%	$217.5205	$217.52	$217.50	$217.50
Purchase #7	$46.77	13.807%	$53.2275	$53.23	$53.25	$53.20
7 purchase totals =	$981.89		$1,077.5624	$1,077.57	$1,077.60	$1,077.50