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	$178.70	11.662%	$199.54	$199.54	$199.55	$199.50
Purchase #2	$85.36	6.418%	$90.8384	$90.84	$90.85	$90.80
Purchase #3	$91.84	5.326%	$96.7314	$96.73	$96.75	$96.70
Purchase #4	$39.88	13.572%	$45.2925	$45.29	$45.30	$45.30
Purchase #5	$199.93	9.718%	$219.3592	$219.36	$219.35	$219.40
Purchase #6	$109.49	12.535%	$123.2146	$123.21	$123.20	$123.20
Purchase #7	$218.37	5.360%	$230.0746	$230.07	$230.05	$230.10
7 purchase totals =	$923.57		$1,005.0507	$1,005.04	$1,005.05	$1,005.00