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	$95.84	4.868%	$100.5055	$100.51	$100.50	$100.50
Purchase #2	$162.58	11.710%	$181.6181	$181.62	$181.60	$181.60
Purchase #3	$233.56	4.442%	$243.9347	$243.93	$243.95	$243.90
Purchase #4	$22.97	11.493%	$25.6099	$25.61	$25.60	$25.60
Purchase #5	$222.95	11.622%	$248.8612	$248.86	$248.85	$248.90
Purchase #6	$233.98	11.366%	$260.5742	$260.57	$260.55	$260.60
Purchase #7	$81.42	12.518%	$91.6122	$91.61	$91.60	$91.60
7 purchase totals =	$1,053.30		$1,152.7158	$1,152.71	$1,152.65	$1,152.70