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	$168.84	7.335%	$181.2244	$181.22	$181.20	$181.20
Purchase #2	$230.79	5.647%	$243.8227	$243.82	$243.80	$243.80
Purchase #3	$108.66	11.781%	$121.4612	$121.46	$121.45	$121.50
Purchase #4	$64.61	8.746%	$70.2608	$70.26	$70.25	$70.30
Purchase #5	$44.27	3.652%	$45.8867	$45.89	$45.90	$45.90
Purchase #6	$180.89	8.678%	$196.5876	$196.59	$196.60	$196.60
Purchase #7	$226.73	7.538%	$243.8209	$243.82	$243.80	$243.80
7 purchase totals =	$1,024.79		$1,103.0643	$1,103.06	$1,103.00	$1,103.10