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	$133.63	6.162%	$141.8643	$141.86	$141.85	$141.90
Purchase #2	$237.78	7.721%	$256.139	$256.14	$256.15	$256.10
Purchase #3	$92.79	9.257%	$101.3796	$101.38	$101.40	$101.40
Purchase #4	$26.68	3.652%	$27.6544	$27.65	$27.65	$27.70
Purchase #5	$27.87	12.388%	$31.3225	$31.32	$31.30	$31.30
Purchase #6	$46.92	12.586%	$52.8254	$52.83	$52.85	$52.80
Purchase #7	$165.26	10.483%	$182.5842	$182.58	$182.60	$182.60
7 purchase totals =	$730.93		$793.7694	$793.76	$793.80	$793.80