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	$41.39	10.150%	$45.5911	$45.59	$45.60	$45.60
Purchase #2	$248.48	4.138%	$258.7621	$258.76	$258.75	$258.80
Purchase #3	$249.28	6.173%	$264.6681	$264.67	$264.65	$264.70
Purchase #4	$10.41	4.333%	$10.8611	$10.86	$10.85	$10.90
Purchase #5	$72.63	10.151%	$80.0027	$80.00	$80.00	$80.00
Purchase #6	$230.54	8.147%	$249.3221	$249.32	$249.30	$249.30
Purchase #7	$172.37	6.430%	$183.4534	$183.45	$183.45	$183.50
7 purchase totals =	$1,025.10		$1,092.6606	$1,092.65	$1,092.60	$1,092.80