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	$128.68	8.416%	$139.5097	$139.51	$139.50	$139.50
Purchase #2	$57.76	5.623%	$61.0078	$61.01	$61.00	$61.00
Purchase #3	$234.44	10.440%	$258.9155	$258.92	$258.90	$258.90
Purchase #4	$92.72	4.286%	$96.694	$96.69	$96.70	$96.70
Purchase #5	$121.69	7.779%	$131.1563	$131.16	$131.15	$131.20
Purchase #6	$205.67	9.577%	$225.367	$225.37	$225.35	$225.40
Purchase #7	$217.43	7.348%	$233.4068	$233.41	$233.40	$233.40
7 purchase totals =	$1,058.39		$1,146.0571	$1,146.07	$1,146.00	$1,146.10