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	$197.97	12.565%	$222.8449	$222.84	$222.85	$222.80
Purchase #2	$82.39	7.432%	$88.5132	$88.51	$88.50	$88.50
Purchase #3	$76.34	3.268%	$78.8348	$78.83	$78.85	$78.80
Purchase #4	$205.68	6.609%	$219.2734	$219.27	$219.25	$219.30
Purchase #5	$181.91	9.214%	$198.6712	$198.67	$198.65	$198.70
Purchase #6	$139.32	9.852%	$153.0458	$153.05	$153.05	$153.00
Purchase #7	$83.33	12.646%	$93.8679	$93.87	$93.85	$93.90
7 purchase totals =	$966.94		$1,055.0512	$1,055.04	$1,055.00	$1,055.00