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	$171.60	5.712%	$181.4018	$181.40	$181.40	$181.40
Purchase #2	$177.73	10.660%	$196.676	$196.68	$196.70	$196.70
Purchase #3	$122.95	11.585%	$137.1938	$137.19	$137.20	$137.20
Purchase #4	$98.73	12.812%	$111.3793	$111.38	$111.40	$111.40
Purchase #5	$171.99	11.704%	$192.1197	$192.12	$192.10	$192.10
Purchase #6	$213.64	9.317%	$233.5448	$233.54	$233.55	$233.50
Purchase #7	$147.57	10.217%	$162.6472	$162.65	$162.65	$162.60
7 purchase totals =	$1,104.21		$1,214.9626	$1,214.96	$1,215.00	$1,214.90