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	$135.92	11.367%	$151.37	$151.37	$151.35	$151.40
Purchase #2	$225.89	6.743%	$241.1218	$241.12	$241.10	$241.10
Purchase #3	$164.87	3.850%	$171.2175	$171.22	$171.20	$171.20
Purchase #4	$226.57	8.186%	$245.117	$245.12	$245.10	$245.10
Purchase #5	$20.96	4.427%	$21.8879	$21.89	$21.90	$21.90
Purchase #6	$112.93	7.385%	$121.2699	$121.27	$121.25	$121.30
Purchase #7	$230.72	7.745%	$248.5893	$248.59	$248.60	$248.60
7 purchase totals =	$1,117.86		$1,200.5734	$1,200.58	$1,200.50	$1,200.60