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	$218.69	13.325%	$247.8304	$247.83	$247.85	$247.80
Purchase #2	$213.41	13.299%	$241.7914	$241.79	$241.80	$241.80
Purchase #3	$50.51	4.649%	$52.8582	$52.86	$52.85	$52.90
Purchase #4	$86.44	4.193%	$90.0644	$90.06	$90.05	$90.10
Purchase #5	$90.58	7.412%	$97.2938	$97.29	$97.30	$97.30
Purchase #6	$202.39	3.567%	$209.6093	$209.61	$209.60	$209.60
Purchase #7	$191.65	4.413%	$200.1075	$200.11	$200.10	$200.10
7 purchase totals =	$1,053.67		$1,139.5550	$1,139.55	$1,139.55	$1,139.60