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	$165.93	9.450%	$181.6104	$181.61	$181.60	$181.60
Purchase #2	$111.54	10.630%	$123.3967	$123.40	$123.40	$123.40
Purchase #3	$173.59	6.782%	$185.3629	$185.36	$185.35	$185.40
Purchase #4	$81.60	11.663%	$91.117	$91.12	$91.10	$91.10
Purchase #5	$9.52	11.636%	$10.6277	$10.63	$10.65	$10.60
Purchase #6	$223.59	4.835%	$234.4006	$234.40	$234.40	$234.40
Purchase #7	$150.95	4.126%	$157.1782	$157.18	$157.20	$157.20
7 purchase totals =	$916.72		$983.6935	$983.70	$983.70	$983.70