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	$110.30	5.432%	$116.2915	$116.29	$116.30	$116.30
Purchase #2	$60.94	11.546%	$67.9761	$67.98	$68.00	$68.00
Purchase #3	$162.27	7.392%	$174.265	$174.27	$174.25	$174.30
Purchase #4	$168.25	7.559%	$180.968	$180.97	$180.95	$181.00
Purchase #5	$248.65	3.181%	$256.5596	$256.56	$256.55	$256.60
Purchase #6	$18.80	12.365%	$21.1246	$21.12	$21.10	$21.10
Purchase #7	$164.34	12.238%	$184.4519	$184.45	$184.45	$184.50
7 purchase totals =	$933.55		$1,001.6367	$1,001.64	$1,001.60	$1,001.80