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	$217.63	10.413%	$240.2918	$240.29	$240.30	$240.30
Purchase #2	$96.87	3.642%	$100.398	$100.40	$100.40	$100.40
Purchase #3	$239.60	9.841%	$263.179	$263.18	$263.20	$263.20
Purchase #4	$55.60	3.638%	$57.6227	$57.62	$57.60	$57.60
Purchase #5	$119.31	7.198%	$127.8979	$127.90	$127.90	$127.90
Purchase #6	$97.96	11.628%	$109.3508	$109.35	$109.35	$109.40
Purchase #7	$189.82	6.693%	$202.5247	$202.52	$202.50	$202.50
7 purchase totals =	$1,016.79		$1,101.2649	$1,101.26	$1,101.25	$1,101.30