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	$88.99	6.551%	$94.8197	$94.82	$94.80	$94.80
Purchase #2	$37.30	7.582%	$40.1281	$40.13	$40.15	$40.10
Purchase #3	$91.65	10.631%	$101.3933	$101.39	$101.40	$101.40
Purchase #4	$123.46	13.752%	$140.4382	$140.44	$140.45	$140.40
Purchase #5	$195.58	9.161%	$213.4971	$213.50	$213.50	$213.50
Purchase #6	$107.51	4.654%	$112.5135	$112.51	$112.50	$112.50
Purchase #7	$53.83	3.739%	$55.8427	$55.84	$55.85	$55.80
7 purchase totals =	$698.32		$758.6326	$758.63	$758.65	$758.50